I have the experience of using Facebook’s domain ads to drive signups and leads for clients. They are in the consumer electronics and higher education space. We ran both Google AdWords and Facebook domain ads for them with the latter delivering better conversion rates and a much better cost per conversion.
@Webinsane ; , when you say cheap advertising, are you referring to CPC or cost-per-lead / signup? If you are looking at cost per lead, then Facebook will be worth a try because of how far you can go with the set of targeting criterias they offer. One piece of advice though, instead of choosing a broad interest like “#Yoga”, go for a much specific interest such as brands for yoga products or famous yoga instructors / courses because you can be sure that only die-hard yoga practitioners fall into these interests.
Hope my experience above helps. Please let me know if you have more questions on FB ads.
By the way, you can include StumbleUpon and Reddit if you are purely looking for traffic to your website.
If your business is local then use Facebook or If it is worldwide then go for Google Ad word, I am using adwords for my two websites and getting better results.