Hi, I'm in agreement with some of the comments in as far as companies are prohibited under B2C acts however it's ok within the B2B environment.
With regards to some of the comments on LF we've worked through a handful of Lead generation softwares, there's this article which is of interest on Lead Forensics alternatives which provides some insight into the differences between this and Whoisvisiting.com (another good tool to use).
I hope the information's of help.
Charlie