Gravatar + Gmail trick = Less spam

Gravatar + Gmail trick = Less spam + added protection of your email address and identity

What to do to protect your email address and identity To solve the identity and spam problem that Gravatar presents, the most effective option is to use a unique email address to register on each website you are a member of. The email address should be hard to reverse engineer. If you use an @gmail.com address, Gmail provides a feature whereby you can append a plus sign to your email address and anything after it is ignored. If your email address is yourname@gmail.com, you can change it to yourname+junkGo

Source: Gravatar Advisory: How to Protect Your Email Address and Identity – Wordfence