Twitter has raised hundreds of millions of dollars in funding, and yesterday it apparently put some of that money to use in making what might be its most prominent, if not largest, acquisition yet.

What did Twitter buy?  Short-form blogging site Posterous. 

Terms of the deal were not disclosed. According to Posterous CEO Sachin Agarwal, “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. Plus, the people at Twitter are genuinely nice folks who share our vision for making sharing simpler.”

So what will happen to Posterous itself? In announcing that his company was being acquired, Agarwal wrote, “We’ll give users ample notice if we make any changes to the service,” adding, “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.”

This would appear to be a not-too-subtle hint that Posterous is not long for this world.

As The Telegraph’s Emma Barnett notes, this may be little more than an acquihire for Twitter. She quotes Tumblr and Instagram founder Marco Arment’s prediction: “I give Posterous less than 6 months before it’s euphemistically ‘sunset’.”

Reading the comments to Agarwal’s post, it’s clear that more than a few users are expecting the same thing. One wrote, “Not good. Not at all. Twitter will be the death of Posterous. You had a good thing going and now you’ve ruined it.” Another lamented, “Well this stinks! Posterous is by far the best blogging platform and now I will be forced to find something else. And as of now, Posterous doesn’t provide instructions on how to migrate to another platform … not happy at all!”

Time will tell whether Posterous becomes a victim of its own success. But regardless, for better or worse, the trend of large ‘start-ups’ (like Facebook and Twitter) buying up smaller successful and semi-successful startups is one that shows no signs of abating.

That puts users of new services in a somewhat precarious situation, raising the possibility that it will eventually become harder for some young consumer internet companies to build relationships with users if users become skeptical about their longevity.

That would be quite interesting if nothing else. After all, in the first .com boom, many of us watched as our favorite startups disappeared overnight after they ‘failed’ (read: running out of money).

In today’s .com boom, it’s just as likely that your favorite start-ups will disappear because they ‘succeeded’ (read: got acquired). The question: is that really much better?