Johannes asked some weeks ago how much downtime someone would be able to tolerate for their OpenID identifier.
I self-host my identifer URL, and a few days ago the server it lives on fell over and couldn't get up. With it being Christmas and all, I've had more important/enjoyable things to do than fixing up my knackered server, so my identifer has effectively been down now for seven days and counting. It hasn't been that much of an annoyance, but it did frustrate me that I wasn't able to log into Dopplr to enter my (admittedly rather boring) travel plans for the Christmas period. I was also unable to give Lifestrea.ms a try, though it does say that it's a private beta so perhaps I wouldn't have been able to anyway.
I think the main thing I've learned from this downtime is that at the moment I really don't depend on my OpenID Identifier for much. The only important thing I've been blocked from doing is my duty of putting the OpenID Foundation board minutes up on the OpenID wiki, though as far as I can tell the wiki's broken right now anyway. In the new year I'm going to look into the most cost-effective way to have my identifier hosted somewhere more reliable while retaining my vanity domain name.