I earn $2k+ a month using PPD. I use AWM content locking and its really simple and easy

Yes, they are work and you can earn pretty good amounts with it!

Yes you could earn a pretty neat income with Content locking, Pay Per Download. You just have to choose the irhgt niche for your product to market.

They do. First hand experience as a customer.

If you have a good product, you'd give your visitors 2 two choice. One is to buy the product, one is to take a survey to obtain the product.
This will encourage users to unlock your product like crazy rather than taking out their Credit Card.

For better rate, you should use direct incentive networks such as Incent.ly, AdworkMedia, CPALead, AdscendMedia, or other incentive networks.

ShareCash or other similar sites are just the middle men. But, they also have their pros, too.

I have never tried to earn money with them, but I understand how they work behind the scenes, and I see no reason why you shouldn't make money with them.

In the CPA industry (Cost Per Action) some advertisers will pay me to have you download their software, get a product sample, or give them your email address.

With most programs like that, I can pay you $2 or $5 to download the software, and the advertiser will pay me $5 or $25 for every person I can get to download the program.

I work for a content locking network, Adscend Media. I would be happy to answer any questions you have about PPD or content locking. Just shoot me a PM.