Go!Messenger, a collaborative effort between Sony and BT offering free instant messaging between PlayStation portables - and BT Softphone on the PC, incidentally - will be no more as of the end of March. The implication from Sony is that while Go!Messenger may have been a decent idea in theory, the implementation wasn't all that popular.
According to a (now removed) post of the SCEE forums: "Although Go!Messenger brought innovative communications features to the PSP community, the service has not developed the base of users that we were hoping for." That's not really surprising; anyone interested in video or picture messaging probably already did so on a PC before the launch of Go!Messenger, after all, so why would they want to change to an arguably less flexible platform?
Sony did say that other products making use of the Go!Cam, little use without Go!Messenger, will be released in the future. If you are using Go!Messenger, you'll probably want to get in as much video chat as you can between now and the 31st of March. Unless Sony changes its mind.
PSP forums (n.b. Link no longer works).