I 'trust' Amazon because its a very classic buyer-seller relationship. I give them money, they give me things. They do a good job of giving me things, I give them more money. Incentives are aligned to benefit me. This is a relationship I can trust to 'do a good job of giving me things'.

I wouldn't say I trust Amazon, but I am comfortable in the relationship we have going on. :)

I am the customer, and I know it. This is not so with advertising-based companies (i.e., Facebook, Google).