By default, picassa accepts only single pictures. However this time I had to upload about 100 pics of Nexus 2010 to picassa and doing that manually, pic by pic was too much of an effort.
The pics that are posted on buzz are saved on picassa web albums. And buzz accepts multiple pictures for upload. Hence problem solved. Upload multiple pics as buzz posts, and they automatically show up in your picassa web album. ;)
A bit of googling got me this very wonderful solution.
Use google buzz.