1) Webdot sends the following request:
GET /friends/graph/alanj.dot HTTP/1.0
LiveJournal sends a 404 in response to that request. It won't send the requested content unless there's a Host header. I'll suggest to Stephen that he add the Host header to webdot's request, but who knows when he'll get to it, especially since he's out of the office for the next two weeks. If we can make the request work on LJ's end for now, that'd help.
2) Webdot has issues; it occasionally gives 500 Internal Server Error on certain graphs for no apparent reason. A new version is at http://www.research.att.com/~north/cgi-bin/x-webdot/webdot.cgi and we should use that for the time being.
3) The AT&T server places caps on the amount of CPU you can use for a graph display request. My friend graph takes about a half-second to render, and I don't have very many friends. Someone with 150 friends and friendofs will probably take 25x as long, and will be very likely to run into the cap. No solution here except to run webdot ourselves (expensive) or make people render graphs client-side (requires Java and some effort setting up stuff to make it work).