Well, Palm is a publicly traded company. Their valuation is fairly objective. HP actually paying more than the market cap of 784 M. http://finance.yahoo.com/q?s=palm&d=t

Groupon doesn't have that litmus test, and valuations and cash money are two different things.

Actually paying $1.2B in cash and stock is different than an investment of arbitrary size with a $1.2B valuation.

Think of it more as, the perceived value way way way down the road of groupon == palm's value as of an hour ago.

An apple and orange may sell at some day at some market to some buyer for roughly the same price. Doesn't make apple == orange.