I'm pretty sure most people know about cookies.
Originally Posted by btarunr
Most sites' functionality will break if you disable your browser's ability to accept cookies, too. You'll get similar prompts.
Which is why browsers evolved to give you the ability to do things like block just 3rd party cookies and erase your cookies after each session. And that happened because after a while, people started to become aware of the risk.
It's also why a variety of tools were developed to deal with them - just like there are now various tools to deal with web bugs, LSO's and a variety of other security and privacy threats. The same will happen for HTML5 and maybe it will be just as insidious as flash. I can only hope that's not the case.