I've tried other sites pix requests, but never really got the BuyRequest.

No great loss as far as I can see.

On several occasions I went out and took photos specifically for requests and posted them. They never got chosen ... fair enough ... but the challenge was worthwhile, and it boosted my portfolio.

However, most of these the requests just seemed to fizzle out. It was never possible to see which image was chosen, so the learning aspect was limited. It would have been good to see which image did win and maybe get a better insight into what buyers are looking for.