Recently, one of my colleagues came to me with an issue he was having with SharePoint. After making sure it wasn't friendly "user error", I determined this to actually be a bug in SharePoint 2010 RTM. Here's the issue:
On your SharePoint 2010 RTM farm, go to your My Site Profile page, and edit it. You are able to change the "Activities I am following" once, and save. But when you do it again, save and double-check, the change was not saved. What gives?!