What is the level of protection against fraud that third-party merchant accounts like 2checkout and revecom offer? Are you satisfied with their fraud protection? Do some of these companies block whole IP blocks?

I'm going to use the list with IPs from http://www-hosting.net/denied.html to block the access to my site, but my only concern is: Is it possible some of the IPs in the list to be search engines' crawlers/spiders IPs?

Thank you all,