I don't care about privacy, but I hate to register and give out my email address if I don't feel it's absolutely necessary to use the product (and if it is, then only if I need the product will I register).

I'm not sure why I hate registering so much (yet another password to remember (or the risk of using the same password on all websites)? or is it completely irrational?) -- but I do, and I guess I'm not the only one.