There's nothing wrong with that. But you never know what will happen to the email address you give to the site.
- Hackers may break into the network and steal the email address,
- it may leak to the web due to some mishap, or
- it might even get sold to spammers.
Don't Use Your Primary Email Address to Sign Up for Anything
This is why it's a good idea
- not to use your primary email address when you sign up at a web site.
- a disposable email address instead,
- an account at one of the free web-based email services, or
- another secondary email address that is not critical.
Do I Follow My Own Advice?
I don't, and I don't have a huge spam problem at my primary private email address.
If you want to have an email address that gets very little junk mail and that friends and other select contacts can safely use, guarding it is a good strategy. Paranoia and mistrust are out of place, though.