[mjevans]

My initial solution would be a restricted trial that is mandatory and lifts when the scheduled subscription date hits and is successful.

The 'trial' period is advertising.

[nkrisc]

Depending on the specific nature of the content (news content comes to mind) you could even just grant access for 24 hours and revoke it if fraud detection fails. This solution wouldn't work well for all types of content where the feature could be abused to harvest static content.