I read on some website that Widows Phone 7 games will all have 200 gamerscore just like XBLA games. The one thing I think is to get achievements and such, they will have to be approved by MS or something. Kinda like how the Xbox 360 is now. It has XBLA and Indie games. So, anyone can release an indie game on WP7, but they won't have achievements. To get achievements, you have to submit the game to MS for certification. Part of the certification process is MS making sure the achievements are a joke.
In my opinion, this has to be done. Crap 99 cent games flooding WP7 could ruin the whole idea of gamerscore. I've read Sony won't allow trophies on the PSP because of how easily the PSP can be hacked. They don't want people hacking every game to get all the trophies and then make the whole trophy system meaningless.