Do site preferences ( blocking npb ) actually work?

[popculturetragic]

As i wait for yet another non paying bidder case to close *sigh*, i have looked through their feedback and noted at least 5 negs in positive feedback in the last few months saying ' never paid' or simular. I have a block in my site preferences that blocks buyers if they have had 2 NPB strikes in the last 12 months. I'd be really surprised if they didnt fall under this category, so i question how they were able to bid in the first place? Anyone else find the site prefrences dodgy?
---------- -----------
My karma ran over my dogma.

[lyndal1838]

Accessing your account from numerous computers is a little different to having a second ID.  And it is not just buyers who have 2 IDs...most sellers have a lot more than 2 IDs, so why single out buyers?

What did the computer tech do for his money?  Surely it was a little more than clear your cookies?