That would fall under the third point. However, they have some big advantages that other companies do not get. For example, if you buy a bad iPhone once, that is really bad for Apple.
Google as a search engine falls under a strange category. On one hand, users put more trust in what they see on Google, making the ad inventory more valuable. On the other hand, if something bad happens they understand it isn't from Google -- something which may not be as clear cut as say, purchasing a defective product off Amazon from a third party seller. (Then there is the revenue that comes for display ads, syndicated search feeds, things that 99% of users had no idea it was Google gaining much of the monetary benefit in the first place.)
On top of all of this a large portion of users who do click on ads on Google have no idea they even clicked an ad in the first place.
Google as a search engine falls under a strange category. On one hand, users put more trust in what they see on Google, making the ad inventory more valuable. On the other hand, if something bad happens they understand it isn't from Google -- something which may not be as clear cut as say, purchasing a defective product off Amazon from a third party seller. (Then there is the revenue that comes for display ads, syndicated search feeds, things that 99% of users had no idea it was Google gaining much of the monetary benefit in the first place.)
On top of all of this a large portion of users who do click on ads on Google have no idea they even clicked an ad in the first place.