[relearn]

As a business, the onus is on you to provide a service that incentivizes consumers to move up from the free tier. If your free trials are being abused, that's an issue with the way your business is structured, not how people register.

You are well within your rights as a business to decline potential customers over something like this, but you need them more than they need you.

[joshmanders]

I'd probably wager if they're going through the process of creating a throw away email and resigning up with it, they need the service pretty badly.