Just be careful with this. Some companies will treat this as if it were a bounced check and keep your debt going.
My experience is internet companies don't collect debt the way you describe. It's the offline companies that do (ISPs, gyms, utilities, banks, etc)
Edit: they also need to inform you before sending your debt for collections, giving you time to get it right with them before any credit score issues. Seriously, people are so worried about keeping their promises to companies that don't reciprocate that concern. Most companies just deal with the consequences of breaking the rules. Why shouldn't we apply the same to them as their users?
I'd imagine this is in the Paypal terms when the company chooses to integrate with them and that 'debt' isn't enforceable