Pos­ter­ous, a start­up that com­petes with Tum­blr in the microblog­ging space, has agreed to sell itself to Twit­ter for an undis­closed sum, the com­pa­nies joint­ly announced today. Launched in May 2008, Pos­ter­ous’ ser­vice is known for its ease-of-use; it bills its plat­form as the eas­i­est and best way to blog by email.

“Today we are wel­com­ing a very tal­ent­ed group from Pos­ter­ous to Twit­ter,” the microblog­ging giant said in an announce­ment. “This team has built an inno­v­a­tive prod­uct that makes shar­ing across the web and mobile devices simple—a goal we share. Pos­ter­ous engi­neers, prod­uct man­agers and oth­ers will join our teams work­ing on sev­er­al key ini­tia­tives that will make Twit­ter even better.”

“The oppor­tu­ni­ties in front of Twit­ter are excit­ing, and we couldn’t be hap­pi­er about bring­ing our team’s exper­tise to a prod­uct that reach­es hun­dreds of mil­lions of users around the globe,” Pos­ter­ous’ team said in a blog post. “Plus, the peo­ple at Twit­ter are gen­uine­ly nice folks who share our vision for mak­ing shar­ing simpler.”

They stressed that Pos­ter­ous’ ser­vice would con­tin­ue to operate.

“Pos­ter­ous Spaces will remain up and run­ning with­out dis­rup­tion. We’ll give users ample notice if we make any changes to the ser­vice. For users who would like to back up their con­tent or move to anoth­er ser­vice, we’ll share clear instruc­tions for doing so in the com­ing weeks.”

Many Pos­ter­ous users left com­ments in response to the post express­ing skep­ti­cism or out­right oppo­si­tion to the deal.

“Don’t like the sound of this at all,” wrote Mark Zahn.

“Twit­ter ruined Tweet­Deck. Bet­ter not hap­pen to Pos­ter­ous. I just spent a ton of time mov­ing every­thing I had from Tumblr.”

Ran­dal Math­eney was even more blunt. “Not good. Not at all. Twit­ter will be the death of Pos­ter­ous. You had a good thing going and now you’ve ruined it.”

“This may sound odd because it’s a free plat­form but I feel slight­ly betrayed by all this,” agreed Ian Cummings.

“I am hap­py for the Pos­ter­ous guys, they get new stuff to play with and I don’t begrudge them that, but I have an emo­tion­al invest­ment in my blog­ging plat­form. I don’t blog much and it’s only for fam­i­ly, but it took me a long time to start and Pos­ter­ous got me going. It’s great to use and now it’s just going to dis­ap­pear and I’m left to sort out the mess. This is the sort of thing that keep peo­ple away from star­tups and going to Blog­ger or Word­Press cos they’re going to be around in 5 years time. Any­way, good luck guys, and thanks for all the fish.”

A Seat­tle-based web devel­op­er, Eric S., was less harsh.

“Don’t like. I real­ly liked the Pos­ter­ous plat­form before the SPACES mod­el emerged, and I thought the mobile ser­vices avail­able for iPhone was a good direc­tion for the plat­form. I have even con­sid­ered pur­chas­ing the third-par­ty iPad app Blogsy which sup­ports blog­ging for Pos­ter­ous, but I’m less like­ly to do so now. Thanks for offer­ing the ser­vice while it last­ed, and best of luck to all of you.”

Oth­ers struck a more hope­ful tone.

“What’s all this pes­simistic talk about Twit­ter ruin­ing Pos­ter­ous?” asked Fran­cois Gui­te. “I say let it be the oth­er way around and hope you guys will improve Twit­ter. Con­grats on your work and many thanks for the great service.”

Hun­dreds of user Pos­ter­ous users, mean­while, react­ed pos­i­tive­ly to the news by “lik­ing” the announcement.

But those users who are unhap­py have well-found­ed con­cerns. Twit­ter has made it clear that the acqui­si­tion was about secur­ing qual­i­ty tal­ent, not adding Pos­ter­ous Spaces to its prod­uct port­fo­lio. Spaces will undoubt­ed­ly con­tin­ue to oper­ate for at least a few more months. But then what? If the Pos­ter­ous team is focused on improv­ing Twit­ter’s ser­vice, who will be left to devel­op Posterous?

Nobody, and that will prob­a­bly result in Pos­ter­ous’ demise. His­to­ry tells us that star­tups that get bought up by big­ger com­pa­nies for tal­ent tend to either go down­hill or get shut down. For instance:

• Gowal­la, which Face­book bought back in Decem­ber, just announced that it would cease oper­a­tions a cou­ple of days ago. Users will be able to down­load their data for a lim­it­ed time.
• Jaiku, a microblog­ging ser­vice sim­i­lar to Twit­ter, was pur­chased by Google in late 2007 and sub­se­quent­ly neglect­ed. It was shut down ear­li­er this year.
• Going, a hyper­local news net­work, was shut down by AOL around a year ago, less than two years after AOL closed a deal to buy it.
• GeoC­i­ties, bought by Yahoo dur­ing the dot-com boom, was uncer­e­mo­ni­ous­ly dis­man­tled and destroyed in late 2010 after Yahoo decid­ed it could­n’t be both­ered to keep it online.
• Deli­cious almost got shut down after Yahoo decid­ed to dis­pose of it, but a buy­er for the ser­vice was found, so Deli­cious con­tin­ues to operate.

An “acqui­si­tion FAQ” post­ed by Pos­ter­ous all but con­firms that Spaces will ulti­mate­ly be going the way of the dinosaur, once Twit­ter decides to pull the plug. It con­tains ques­tions like “How can I back­up or export the con­tent of my Space(s)?”, “What hap­pens to my con­tent if I don’t do any­thing to my Pos­ter­ous account?” and “I bought a cus­tom domain from Pos­ter­ous – what hap­pens to it?”.

When Pos­ter­ous clos­es down, it will hard­ly be the first blog­ging plat­form to set its users adrift. For exam­ple, Google alien­at­ed a num­ber of long­time Blog­ger users when it decid­ed to dis­con­tin­ue FTP pub­lish­ing a cou­ple of years ago. (We used to pub­lish The Advo­cate this way, but now we have our own Word­Press instal­la­tion, which is total­ly under our con­trol. We could­n’t be happier).

And Microsoft pulled the rug out from under its users when it dis­con­tin­ued MSN Spaces (lat­er Win­dows Live Spaces) — though it did pro­vide Spaces users with the abil­i­ty to trans­fer their blogs to WordPress.com, Automat­tic’s host­ed Word­Press ser­vice, for a lim­it­ed peri­od of time.

We actu­al­ly con­sid­ered using Pos­ter­ous to pow­er our microblog, In Brief, before we launched it in 2009, but we ulti­mate­ly went with Tum­blr, which has expe­ri­enced phe­nom­e­nal growth since we began using it back in 2009.

How­ev­er, our expe­ri­ence with Tum­blr has­n’t been that great. Tum­blr sim­ply has­n’t improved its ser­vice to the extent we were hop­ing it would. We plan to move In Brief over to Word­Press as soon as Word­Press has bet­ter microblog­ging sup­port, which will hope­ful­ly be the case with the next release, or the one after that.