The LeadLander product seems to identify users by company name (most likely by checking the IP address/netblock) and then "integrates" with LinkedIn and Jigsaw in order to contact (spam?) the users by email (see: http://www.leadlander.com/web_analytics.asp).
Definitely interesting, but legal? Not very likely...
There is nothing in the US that makes this sort of activity illegal. The exceptions would include minors, health or certain financial information. Excluding that, unless it goes against something stated in their policies it is perfectly legal in the US.
That's just a guess on my part. I'd love to hear from someone better versed on the law about the legality of that email.
Opt In is a cultural idea, not a legal one.
f :: IPAddress -> [Maybe EmailAddress]