> I also like to see who’s advertising because it shows which industries/companies compete on marketing, instead of their own merits.

Quite frankly this is wrong. You can have all the merits in the world, but if people don't know about it then you're out of business.

> It really shows which products have high marginal profits.

AdWords can be life or death enough that it's worth eating the cost because the alternative is not having a business.

> You can have all the merits in the world, but if people don't know about it then you're out of business.

With the rise of social media, this is about 20 years out of date. If you have a great product and 100 users, 1000 people are going to see glowing testimonials at zero cost.

I strongly disagree. You're thinking purely from a software point of view - advertising is still extremely useful for any kind of local business or startup.