Well I don't know about Bearshare, but Gnucleus has a habit of retrying "dead" hosts pretty much forever, regardless of how many connection failures it gets.

So if someone's nucleus client tagged you as a potential source for a file, you will keep getting pinged by that client until

a) The download is finished (which could be days later)
b) The user cancels his download and re-starts it from the Partials section of the client, thus resetting all sources to 0.

If you have a static IP, Gnucleus clients trying to use you as a source can become a serious nuisance. The bug has been there pretty much forever but for some strange reason no one seems to take it seriously enough to get rid of it.

From the user's standpoint, the bug means that the longer the client is used (regardless of restarts), the more dead sources it accumulates for its downloads, increasing the ratio of "pointless" connection attempts to valid ones and generally making the download harder to complete, which in turn allows it to rack up even more sources etc. etc.

But don't try and mention this in the Gnucleus forum - You'll be flamebait in no time