I have no experience with CPA (at all), but do have experience selling digital products online (e-books, to use an increasingly dirty word ). They are all in different (non-IM) markets and, although conversion rates depend on the traffic source, all do pretty good.
However, I'm guessing conversions for CPA offers that don't require upfront money are always going to be higher than for stuff that does.
I know (think) that places like CPALead will let you provide digital content to people that fill out surveys, etc. I imagine setting things up to do that is relatively easy, and significantly higher conversions would (or could) result in greater revenues than with stuff that requires money upfront (in other words, less money but more transactions vs. more money but less transactions).
However, I'm wondering how incentivised CPA offers are received by the online public?
For example, do they require extensive explanations about why it's "free", what will be done with their personal details, etc.?
In other words, the idea sounds great in theory, but how does it work out in practice?