Question : Search relevant web sites for email addresses - feasible?

I have a client who wants me to find a way to search the web for a particular phrase having to do with a product he makes, then collect email addresses from the sites that are hits so he can send them info about the product he has. I know this sounds like SPAMMING, but he is certain many of them will want his product once the know about it.

I am sure his has been done but I need to know first, is it actually feasible, second, is it a legit way of getting leads, and then, if so, how to do it.  

Your thoughts?

Answer : Search relevant web sites for email addresses - feasible?

I am not sure I agree it is spamming in the worst sense.

If a website sells Aluminium frames and this guy has come up with a super aluminium framing system, a PERSONAL email to the marketing or info email address could be considered an inquiry.
If I for example get an email from a culture web site suggesting I put my culture website on their links page and reciprocate, I may or may not do it but I do not consider it spam.
When I get an obvious templated standard link request to put my culture website on someone's tractor pulling website, I report it to spamcop.

But that is me

Gathering email addresses using spidering or whatever is not spamming until the email is automatically sent without being sure the recipient is relevant to what you are selling.

http://www.google.com/search?q=email+spider