Anyone use the 'Fully Paid Lending' program?

Looking for opinions on this program as I've seen it advertised a bunch. Who might this be right for?

Let's say I own 1000 AMZN shares, I can elect to 'lend' 100 of those and receive income while they are 'borrowed' from me? Meanwhile I can recall at anytime and sell if I wanted to?

If this is true, why would someone on the other side do this instead of buying their own?