In my opinion, Megabus was great. I guess ridership was low and gas prices are high, so they decided to discontinue service on the west coast. But there is an alternative. The California Shuttle Bus offers service from San Francisco to LA for comparable rates, even offering $5 seats if you're lucky enough to find one. I haven't tried them yet, but I thought I'd share the info.
http://www.cashuttlebus.com/

