Twitter has caused an issue with Facebook. It doesn't matter whether or not you have the Friendfeed or Twitter applications, they are posting on your wall. Since this is such an issue, it is now a trending topic. From this, so many people have replied to the mashable.com tweet that their site is affected now as well.
Twitter is eventually going to join with Google and form Skynet. At this point that is not the case. Just be careful as to what tweets are on your wall.