Adhesive vs Welding

So while on the hunt for information on Fusor 800 seam sealer I ran across this little nugget.

http://www.nastyz28.com/forum/archive/index.php/t-4293.html

My initial reaction was to curse GM guys for their idiocy, than point and laugh the way American auto guys do to rice. I mean seriously doors? FLOOR PANS? Quarters? My roommate and career body guy heard my cursing and quickly informed me of my ignorance. Apparently many manufacturers including high end cars like Maserati are bonding body panels now, he told me of tests they'd come in and do where the adhesive would hold beyond what the surrounding metal could endure.

I'm still not sold, there has to be a downside that I can seem to find, otherwise body shops would all sell their welders. The one downside I did find was heat seems to be the devil to this stuff. Now i'm not sure whether i'm looking at the data sheet for the correct stuff, however this one seems to indicate that as low as 180deg(Needles CA will see 130) the bonding shear strength dropped dramatically.

http://multimedia.3m.com/mws/mediawebserver?66666UuZjcFSLXTt4xMcNxT2EVuQEcuZgVs6EVs6E666666--

No I'm not planning on welding the floor pans in the Fish, just extremely interested in unbiased strengths and weaknesses of both methods.