Registering on web sites can certainly get your name added to "spam" mailing lists.
While sites like Amazon, Tesco etc are good at NOT handing out your email address, other sites ARE willing to sell on email addreses, and job sites come under that category.
I think you should have AT LEAST 2 or 3 email address, for different reasons.
Keep one ONLY for family & friends and NEVER give it out to anyone else.
Have another for registering for web sites (maybe more than one).
Another for interent banking and so on.
I have about 6 different email addresses that I use for different things.