Once your IP somehow made it into the gnutella network it can be cached for weeks and you will receive connection requests every now and then until the last gnutella node has forgotton your IP. If you have a dynamic IP and someone else who is regularly running a gnutella client is subscribed to the same ISP for example (so he used the same IP running as a gnutella client) you will always receive a few connection requests every now and then.

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Morgens ess ich Cornflakes und abends ess ich Brot
Und wenn ich lang genug gelebt hab, dann sterb ich und bin tot

--Fischmob