I hate it, when sites make me register. I hate it even more when they refuse a mailinator address. Because then I have to use a throwaway yahoo/live/gmail whatever address and its yet another step to log into that one to get the activation link.

What is an example of a site that needs to refuse users that use mailinator and co?

If people buy things on your site, you don't want them to get locked out because they forgot their email or use a shared email address.

Every time you give something for free after a user registers.

Other than "the service" which often relies on users as much as users rely on it; what are you talking about specifically?

Hi there, for different projects, I had to prevent users to register with disposable emails. So in order to have a centralised domain list, always up to date, I made a small API.

I maintain the list of disposable domains myself by doing monitoring and using custom crawlers. Feedbacks appreciated :)

Interesting API, but this will probably end up as one of those "It helps" things.

What guarantees you won't sell emails you collect ?

If you don't trust me, you can use the domain method. This way you don't send the email, but only the domain :)