Great question XBLElec,
I suppose it would depend. I would say it's not worth the investment if all you are doing is getting people to visit the site. If that is the case your money would be better spent on highly targeted PPC traffic.
If you are getting people to leave information (i.e. name, email, phone number, etc) for remarketing purposes, then I would say it's worth a shot. That assumes that what you are giving out appeals mainly to the market you want to target.
Take this example. If a company wants to generate an email list and that company is in the business of selling retirement financial services, it may not be the wisest idea to offer a freebie with such broad appeal that people who don't want their services are getting it (ie. An iPod touch or something like that). On the other hand if they offered a free hour of financial planning advice, then the people that responded would be very valuable to them.
Basically you have to think about whom these people are and what you will do with them. Don't just give stuff away for visiting the site. Ask them for something in return whether it be to like a Facebook page or follow some other social account or give you contact info. You also want to make sure that the freebie you are giving out attracts people that you can market to later and not just anyone who may or may not want your services.
This blog post has some good tips,
http://ameenafalchetto.com/giving-free-stuff-blog/
Hope that points you in the right direction,
Shawn