Actually, some of those ipod4free type sites are indeed legit. Where I work, a potential customer's email address is worth actual money. By keeping in contact with said customer(s), offering special discounts, bringing certain items they may be interested in to their attention, you end up with a conversion ratio of about 20:1. Twenty people (who are indeed in the general market for the types of things you deal with) read an email, one of those people buys something.
With honest companies (like the one I work for), it's really not spam. I maintain the email list, and we do indeed have proper "Click here to unsubscribe" links on all our emails. Heck, we're still small-scale enough that I can deal personally with the morons who don't click on that link but instead email saying "Please unsubscribe me"; there's no point in us retaining someone on our list who's angered every time he receives an email from us he doesn't want.
Anyway, I got a bit sidetracked there. The point is, it's very logical to offer the equivalent of $300 in free gifts to someone if through that person, you will get the (valid) email addresses of, say, 10 potential customers. Those 10 customers won't make $300 worth in purchases immediately, but in time, with a proper marketing strategy, they
will purchase items from you, eventually leading to way more than a measly $300 in sales.
The main challenge to honest businesses is how to keep from being percieved as yet another spammer. With us, we're still so small that we do indeed have personal relationships with our customers... quite often, a customer would call our 800 number in the US, which used to forward to our office here in Jerusalem, and end up yapping away with my boss for hours about life, the universe, and everything. My boss and the warehouse manager went to Indonesia to help with rescue efforts there, which was another great thing for us
to be able to report on and keep that personal rapport with our customers.
So anyway, yeah, this kind of offer can actually be quite valid.