Software modifications or "improvements" are standard practice, and often essential to maintain or grow a customer base for a product. Facebook, it would seem, makes more head scratching modifications than anyone, forcing what they consider to be better upon their users. This of course results in significant community outcry, the majority of which, ironically, occurs on Facebook. You may have noticed a modified chat pane on the right side of your Facebook page. Rather than show only your online friends, suggested chat partners are chosen for you. Here's how to change it back:
A clever fellow named Tal Ater, who likes to dig through Facebook code in his free time (wow), has produced a nifty solution to save you from your chat sidebar woes. He's created this bookmarklet: Fix Chat which you can drag into your bookmarks toolbar and click every time you want to fix your chat.
If you're on a Windows machine, there's a automatic fix you can download here. He's working on a similar script for Mac and Linux.