But they're not doing a good job in blacklisting debit card providers (providers that let you generate your own unique debit card number and start a free trial

But they're not doing a good job in blacklisting debit card providers (providers that let you generate your own unique debit card number and start a free trial on this new card, resulting in using the service for free) or banning shared accounts (i.e. 4 people meet on the internet only for the purposes of buying one account).