LiveJournal has taken to using a Content Delivery Network (CDN for short) to serve its userpics. This means that instead of all 197 of some permanent user's userpics being served from LJ's servers in Montana, no matter where you are in the world, the CDN will try and have them on a server that is geographically much closer to you. This means that the master copy of your userpic is stored with LJ, but you are actually viewing a copy on the CDN's server.
This ... can lead to a bit of a situation, because now people have started to get served incorrect userpics from time to time due to the CDN's local copy being bad. It's worse than just a completely wrong userpic -- since it's only on one CDN server, your best friend halfway across the continent is looking at a different server, sees the correct userpic, and thinks you're on crack. There is a treatment, but the cause (why the CDN grabs the wrong picture, why it chooses the wrong picture that it grabs, whose stuff is broken, and exactly what piece of programming or equipment is broken) is, as far as I know, unknown at this time.
As seen in metaquotes, and as I explained there:
There's growing support for a mob with baseball bats and/or code machetes fixing the userpics problem. On the one hand, it's good to have the userpics served from someone else's more geographically convenient servers. On the other hand, if they're going to store the wrong userpics for a certain segment of the viewing audience...
Basic rundown of what happens, for those who aren't familiar with the problem:
LiveJournal: 197 userpics is a lot! Ow, my bandwidth!
Content Delivery Network: We can help with that!
LiveJournal: Great! *sets stuff up*
Content Delivery Network: *retrieves original userpics from userpic-origin.livejournal.com* *copies to p-userpic.livejournal.com* Have your userpics, people!
User: Dude, that is not my userpic.
User's friend: What do you mean? That's the same userpic you've had for three years.
User: I'm telling you, mine is supposed to be the O RLY owl, and I've got Goatse!!!
User's friend: Believe me, it's the owl. I would have noticed Goatse.
User's neighbor: WTF, man. Your goatse userpic just showed up on that post when I was showing it to my MOM.
User: SEE!!! *screencaps* *goes to support*
Support: Oh god. Another one. *gets link to userpic* *bothers staff*
Staff: *whacks content delivery network a few times until it drops the goatse userpic and gets the O RLY owl from userpic-origin.livejournal.com again*
Support: There! Fixed! (Until the next time, when My Little Pony gets replaced with naked Amanda Tapping!) *drinks heavily*
It's not necessary to include a screencap when reporting. We know it's happening. You don't have to prove it. Just grab a link to the affected icon, or include its keywords, and let Support know so that Staff can go run the pound-on-the-CDN-with-baseball-bats-agai
[Edited to add 2009/04/04: LJ has since switched Content Delivery Networks, and, surprise surprise, this doesn't seem to be happening anymore.]