I was just responding to John Blackbelt Jones's message about requerying the network when a download fails -- it's a good idea in theory, but it's just always a little dangerous to put in features that automaticaly increase network traffic without the user explicitly initiating it. So, it just requires some careful thought, which probably would mean only applying it in very specific situations.

As far as passive searching, that's another issue entirely. It is also a potentially very valuable feature, and could reduce network traffic considerably. We conducted some thorough studies of this about a year ago now, however, and at that time the network was too dynamic for cached query replies (the message that responds to a file hit, a little different from a PONG, but sort of similar) to make that much of a difference. We could revisit this issue at some point, however, as the basic idea is inarguably sound.

I don't know if you do any programming in Java, but it might be interesting to take hack up the source a bit and try to quantify again how effective this could be. UltraPeers in particular could change the effectiveness of this.

Oh, and sorry I keep not logging in on this thread -- I keep forgetting that I haven't logged into this site yet on my girlfriend's fancy Titanium. =)

Thanks.