[contravariant]

I'm not sure the first type of advertising is that useful. Why would I care which plumber paid Google the most money? I just want to find plumbers.

I suppose you could make a 'search' engine by just letting people pay to show up on whatever keyword, but I'm not sure if that serves the same purpose as a general web search engine.

[Spooky23]

It’s a sort of social proof. If you want a larger company to reduce risk, you can probably correlate placement with revenue.

In the Yellow pages, display ads were the same thing. If you don’t know of them before hand, you might assume that the half page display ad was a more “legit” company than “AAAAA-1 Plumbers”.

[passivate]

> Why would I care which plumber paid Google the most money? I just want to find plumbers.

Yes, exactly! Also, To your second point, its in Google's interests that customers have no other way except paid ads to look you up. IMHO, Google has become a company that wants to install toll booths on the internet.

[bigger_cheese]

Businesses have to pay to advertise in phone directory already so I don't think this is much different and as other commenter suggested presence of a paid ad suggests service provider may be more reputable.

[passivate]

Sure, but then the framing is "we're just as bad as these other guys".

[lordgrenville]

> Why would I care which plumber paid Google the most money?

I agree it's a bad metric if you have a better option, but in this example you don't.