I did the clearing and the reset and it did happen again. I was exited out of Safari. It seems to be happening when I am putting the screen back to normal with my fingers in the screen. I have always made the screen (text) larger and then put it back to normal without a problem but for the past couple weeks it now exits me out of Facebook. I have not noticed it happening on any other site. I do not use the mobile addition of Facebook and never have had this problem. The mobile version is too difficult to actually use. Not a fan. I don't think using the full web version is the problem because I have always used it without a problem.
I have the iPad2, 64, 3G, the iOS was up-to-date until the iOS 6 release so it is 5.something, and it happens at home and in the car using the 3G, so I doubt it is my wifi. I have plenty of space available, and don't think that would play a part either, but just in case someone asks thought I would throw that in.
I have had it happen when that is the only tab opened as well as the three tabs I pretty much always use for the three sites I visit regularly. Again, even with all three tabs in use, that is not unusual and have always been doing it long before the last couple weeks. Nothing I do has changed in the last couple weeks. I have not dropped my iPad nor have I spilled anything on it. I take extremely good care of it.