With news of Unroll.me selling user inbox info to Uber, lots of people are repeating "if you're not paying for it, you're the product."
I've said before, and will continue to say, that that is the wrong formulation. Sometimes you pay for it and you're still the product – look at US ISPs. Sometimes you don't pay for it and you're not the product – free software.
The real question is whether a software or service empowers users, which can't be boiled down to whether you paid.
@rysiek I'm with you 100%. "if you can't figure out the business model, that's a pretty good indicator that you're what they're selling" might work, but it needs some workshopping.