the problem is often unlimited free trials == subsidized by paid customers.

I'm sure if Heroku, for instance, was a paid product without free trial,it would potentially cost less to paid customers. This and services like mongohq,mongolab,... clearly subsidize free accounts with paid ones.

I think the amazon free tier model is a better model.You have one year to mess around but you still have to pay if you abuse resources.

Of course in the podcast hosting space,things are different since there is a lot of competition. Not that much in the paas market,where good services are rare. Most paas suck,we all know which are the good and the bad ones.