There have been few incidents recently where a customer subscribed for Unlimited Resume Views, using Paypal. System has automatically provided him access. Customer utilized the Resume access services for complete subscription term. And just a day before subscription renewal date, he not only cancelled the subscription but also filed a chargeback for amount already paid, giving the reason "Unauthorized Use". Paypal also reversed the payment immediately and open a dispute case.
In this way, customer has utilized the Unlimited View Resume subscription services for full one month and has not paid anything.
Paypal policy also says that if there is no tangible good to be shipped then seller protection is not there. It means, using paypal for "services" (instead of "product") is at the risk of seller.
I would suggest talking with a lawyer.
From my point of view (and I tend to use the common sense viewpoint) is that BOTH the subscription and the ads are a product and not a service. Computer data has been held (by US Courts) as tangible product in several cases, and unfortunately I can't quote specific case history.
So again, find a lawyer.