I'm careful who I give my personal email address to so I don't get much junk mail. Many stores ask to add me and I just 'no thanks' at the checkout counter. Some stores also ask for your phone # and I never give that out either. Phone spam seems far more prevalent then junk emails. If caller ID shows a number we don't recognize, we let it go to voice mail. Have NEVER had any spammer leave a message since they obviously know you won't be calling them back.
When shopping online many offer the option to checkout as a 'guest' and that also avoids random stores from gathering emails they likely turn around and sell to others. Particularly a store I might only shop at one time or very infrequently, there is no reason to give them my email address. Have found a few online shopping sites that won't let you look at their merchandise without first providing an email for 'verification'.............ummm no thanks, plenty of other places to shop online.