Friends and family get one to use. Another for sites you use credit cards and banking. Another as a junk address for signups at forums, news sites, etc. That way if one ends up getting spammed badly, you can just change it and not affect the others, which is usually the junk address that takes the hit.

If you pay $10 on average for a domain of your own per year at a registrar site and add email services to it, you could have 50 email addresses allowed and that way other than friends and family give each site a unique number up email address, like me@mysite1.com, me@mysite2.com. That also will tell you who is selling your email. You can have all those incoming forward to a single account if wanted for easier use.