I'm seeing lots of people subscribing with their real email address to different newsletters or random websites that they might use once in a while.
For a couple of years I have run a proxy SMTP that I kept to forward emails to my real address, as a privacy measure.
People tend to use the "+" sign in order to identify if their address was sold, for example signing up with "michael.john+amazon@gmail.com", now what most do not realize is the fact that when selling data to third parties, most companies parse their email lists and clear our those "+" sign. (Source: I have worked with companies that do that)
I found the relay from Mozilla to be massively useful in this case, so if anyone is interested, have a try with it:
As a side not: If you're using firefox, it integrates nicely into your browser, right clicking on a field and selecting "Use relay mask" is enough to generate an instant address so you can easily rotate them for each service.