From: http://maxklein.posterous.com/

So you have somehow begged, borrowed or stolen an email list of 1000 users who you believe are interested in your new service. Would it not be great if you could somehow convert that list into real people, with real photos, and perhaps even more concrete information like “My service has a higher than average gay consumer group” or “My dating service seems to be very popular among 9 year old girls”? Such information can help you correct course before you are too invested in a particular idea you have.

Well, a few weeks back, we were handed down this lovely present by our masters from above: Facebook. Save your email list as a CSV file (just comma separate those email addresses). Upload this file to your facebook account as if you wanted to add them as friends. Voila, facebook will give you all the profiles of all those users (in my test, about 80% of my email lists have facebook profiles). Now, click through each profile, and because of the new default facebook settings, which makes all information public, about 95% of the user info is available for you to harvest.

If your email list is too large, then use the very same CSV file and upload it to mechanical turk (a list of 10.000 would cost you about $10), and ask the mechanical turk guys to gather this information for you.

After you have all the demographic information you want, try to do good with it. My personal advice to facebook users: Switch on your privacy settings, make your friendslist private. Business want this information, and facebook has given it to them.

Update (from a reddit comment): Use this URL http://www.facebook.com/search/?ref=ffs&q=name@domain.com&o=2048&init=ffs and screenscrape for even more spammy goodness.