Say you want to invoke a remote web service deployed on a server that requires SSL. Say, the maintainers of the server couldn't (ot could not be bothered) getting a real, shiny, authetic, SSL certificate signed by a real CA. Or - more likely - let's say you are the one developing the service and the service consumer, and you don't have a valid certificate for each of your development machines (as you may know, ssl certificates are specific to a machine).
Problem: your http client used to access the service will never pass the ssl handshake.
Solution: see here: http://devcentral.f5.com/weblogs/joe/archive/2005/07/06/1345.aspx for a real life saver