Yahoo may not be in the dotcom glory days boom phase, but its not going away, and it has some increadibly smart people. I know somebody vaguely who worked in europe on Yahoo backed stuff and it was front-line innovative work.
Amazon is huge and complex and has many rulers and conflicting rules, and also has this nasty 'Screw the worker' back-taste about how you, the digerati get the candy, but the people in the warehouse are urinating in bottles to make pay.
Do you really want that on your personal live choice resume?