Posting what I've read elsewhere:
"I played this with a bunch of people last night when I inadvertently discovered that I could lag out an entire server (or at least an entire area of the server). At one point, one of the guys I was playing with said that you could nest backpacks within backpacks, like Russian nesting dolls. He said there didn't seem to be a limit to the number of times you did this. Well, he only braved a backpack within a backpack within a backpack. I foolishly kept going, and managed to be 5 backpacks deep. After this happened, whenever I tried to log into a server, everything would freeze. People stopped moving and you stopped being able to use items. Everybody I was playing with kept trying to server hop complaining about the terrible server performance before I realized that it was me. I was bringing everything down when I tried to connect.
I eventually decided to join one of those high max population hosted servers, hoping that they would have more server resources to handle my fucked up inventory. It took about 5 minutes after I logged in before I could equip my weapon. It took at least another 30 minutes to unfuck my inventory. I had to place a backpack on the ground, then proceed to un-nest all of them. After they were all un-nested, I discovered that I couldn't pull items out of them and into my inventory, but I could pull the items out and place them on the ground. So I eventually emptied all my backpacks onto the ground and waited. After a very, very long time, the server eventually unfucked itself and I was able to reclaim some of my items. The whole time this happened I had a yellow connection icon.
So there. I inadvertently discovered a lag bomb. I don't know if it is area based, or if it affects the entire server, but it is deadly to all involved."