While that's often true, many (most?) users have no idea that they're making this deal (i.e. "I let you store your cookies on my computer and in return I get free stuff.").

The European "cookie law" has caused many websites to give better notice that they're planting cookies, but it's rarely clear how those cookies are being used.

There is a better way. What if I purposefully signaled my intent to potential sellers, rather than having them guess what I want (based on their data about me)? Amazon wish lists are an example (although they'd be better if I stored the list in a place of my choice, where I control who sees what, and I'm told who looks). For more on this idea, see:

http://en.wikipedia.org/wiki/Vendor_relationship_management

Let ad companies and ad supported SaS do what they are good at - Targeted ads. Target people who want the ads. Give those people the services of easy access to new products, and leave people who do not click on ads alone.

There is a simple answer to all this. Its called opt-in. If you need to harass and track users who do not want ads, then either the targeted ads are not targeted enough, or its a failed business model. Time to show which one it is.