I think you are missing the point though, first and most importantly in its current state Motorola Mobility is only worth maybe 13 billion at most, and no one would ever pay the face value for something in the corporate world; however Google's offer 12.5 billion is coming very close to paying the actual value, which shows they really do care about increasing their patent portfolio.
Some other things to consider 63% increase in share value is HUGE for a company who has been seeing shave values drop. I can understand wanting to be greedy but investing in companies is, in some ways, like playing poker you have to know when to go all in and when to fold, but more importantly you have to know when to walk away from the table. Also keep in mind you, as a share holder, should see the values of your stock go up some before the end of september due to this announcement and the release of the Droid Bionic, at that time it might be wise to sell your shares. Just with the announcement from Google the share have jumped nearly 57% however this wont last and as the deal approaches share values will decrease drastically.