[bigiain]

Depends hugely on the SAAS and it's current and desired customer base.

But some obvious candidates are

1) discontinue free trials.

2) provide enough obvious value to convert the current funnel of free trials into paying customers at a high enough rate that you don't care about the "freeloaders"

3) radically differentiate the support available on free trial accounts.

In the long run, and dev effort/time spend integrating email domain blacklists is just time taken away from building features that add value to the service/company. It's only possible that spending that time adding features will turn the conversion rate up, but its guaranteed that fencing off the top of the funnel will reduce the number of conversions.

[Handytinge]

A comparison of the dev time to check a value in an array and modify your entire business model is absurd.

Mitigation against abusers of a service is a valid strategy.