i get it, you cant be a good large company without buying your competitors. it does make sense. and yes I am aware of the scenarios you provided.
The difference IMO is that those companies while they acquire, they still innovate. I am ignorant of yahoo post 2004 or so but i havent seen any real innovation from them, even on their acquisitions. Years ago i used to LOVE yahoo games. simple layout, easy to get in. Sometime though it seemed that the yahoo home page turned into its own geocities page. too much clutter it was very hard to actually find anything you wanted and i havent really been back since
I would love to see yahoo keep going for another 20 years, but i dont want to see them pull a radio shack either