Email Alias or New Email for every Project

How should the mail setup be done If you have several projects?

example 1:
Tie1 : Articles
Secondary Links: Blog/Image/Forum..

Assign ONE Email to both? Assign two mails to both? Assign an alias-mail to the secondary?

second:

what happens if I use the email from Tier1 on other projects:
Some websites should reject a new register?

you can use the same email but it's always better to use a separate one to avoid footprints.

If I do Forums or BC then that email address is dead after the first use for me. I usually change it every time, it takes about 30s to register a hotmail account

so better one mail with pop for every project then.

one email per project?

what happens if i use the same email account and for sites like doc share?

would they try to login to the same account as created in the first project for the second project?

The same email is not working to create a second account on the same site. Thats the only limitation here and a reason to use either a catch all email or a different one.