Popacular, a site that measures popularity of websites according to the number of related tweets, has a huge counter that counts the overall number of tweets. I don't know how accurate this thing can be, given that it's third party, but if it is, then we've recently surpassed the billionth tweet mark.

This is just another sign of how big Twitter has become. For comparison, Facebook recently announced they host 10 billion photos in their database; however, Facebook is huge and has been around much longer than Twitter. If anyone ever needed a clear sign that Twitter has gone mainstream - however you define it - this milestone is it.

Also, seeing that counter spin amazingly fast makes us sorry for all those times we've made fun of Twitter's engineers for not being able to keep the site up during a traffic rush. Sorry, guys, we understand now.