It would seem that del.icio.us has joined Technorati, Feedster, BlogPulse, etc. in the Web 2.0 applications that don't scale very well. Posting new links to del.icio.us seems to fail for me more times than it succeeds.
Not surprising, I guess. Anything with a central server is gonna hit scaling problems if it gets popular. Time to dust off all those old P2P treatises from 2001. :-)