When the computer boots, it asks for the keyring password in order to automatically connect to a wifi network. This way, it is really dificult to set the system to autologin and automatically connect to the wifi network, start an internet application (mostly p2p, could be any server) and have it running.
It would be nice to be able to connect to a wifi network without this prompt. Maybe the solution is to chose not to ask this specific question ever again (yes, windows-style), or to store some user-specified passwords in a publicly accesible keyring.
I think this behaviour could be related to bug #137247 (libpam-keyring broken on autologins):