Microsoft is under assault in every direction, and losing the battle on any number of fronts. That's why it's so desperate to come to terms — any terms — with Yahoo. The software giant went back to Yahoo yesterday to suggest a joint venture that would give Microsoft a position in Yahoo's search business. We're supposed to believe that Yahoo — thanks to Carl Icahn's proxy battle to replace Yahoo's board — is feeling the heat. But it's Microsoft that has everything to lose here. The barbarians are at the gates, and Gates (as in Bill) has gone off to serve humanity. Without a search strategy that works — and with Yahoo potentially linking up with Google, a partnership that is expected to be announced in a few days — Microsoft is an empire in rapid decline.