Although the outages are very short, normally only a few minutes, they keep increasing. On some games, like CityVille, it's even more annoying, because you can lose some of your last actions made there.
No need to say that while you Chat with someone, it's definitely not fun. To that, there are some technical problems, too. The online status can hop from online to offline back and forth. I often need to reload the page to see if someone is still online or not. I'll guess this also has something to do with the games, as they need some time to load the chat-bar below.
And I also discovered that sometimes, a part of the site like the chat or something else is missing or not reachable. I tried for minutes to get to my messages. And guess what, it happens on the prime time usage a lot more often.
Looks like Facebook need to stack up some serious server power. Once it was the big premise of Facebook to never have an outage. It's big now, and the problems are growing. But the more we rely on services like Facebook, the more important it is for that service to keep being reachable at all times.