Maybe they have too many products

from here and here

Look, I know all software needs to be patched on occasion, and I know it's better that it gets patched than if it doesn't, but there are just soooooo many Microsoft patches! I can't be the only person who tires of hearing about them.

Look who thinks they won the browser wars

from here and here

Who's looking forward to seeing their ad blocker get lobotomized? That seems to be where we're headed if Google has it's way. It reminds me a little bit of the controversy over PatchGuard in Windows Vista years ago. A security mechanism was added to the system that blocked access to functionality that malware and security software alike made use of. 

Google's new extension system will basically be doing something similar, with ad blockers getting the short end of the stick. One of the big differences here, though, is that Google is the world's largest advertising company, so they will definitely have an incentive to not make exceptions for ad blockers, even though those are an important way to block malware online.

If ad blocking performance deteriorates too much in Google Chrome in comparison to other browsers, though, Google is going to start losing their dominant position in the browser market.