The arguments about the Goozex economy are entirely valid. By putting more points into the system (creating more demand) when there is not any change in the amount of games available (low supply), they are deflating the value of their currency. Supply needs to fluctuate with demand, not remain fixed.
That said, Goozex did do something to combat this, though it seems I'm the only one who noticed it. They implemented a system that automatically adjusts most game prices to the point equivalent of the current going rate on the Amazon marketplace. This primarily only applies to retro/PS1/Xbox/PS2 titles, though, as it looks like demand still determines the prices of titles for the PS3/360/Wii. This is why over the last few months game prices have risen drastically across the board.
In regards to not being able to get new titles, I do my best to put newer things into the system having just traded a smattering of more recent releases (3D Dot Game Heroes, SMT: Strange Journey, Alpha Protocol on 360 and PS3, NSMB Wii, Super Street Fighter IV, etc.). I use Goozex primarily to get older games and have had no trouble getting stuff and using my points (I've received 446 items in my 2 years on the site).
Also, about 70% of the 176 games I have sent out have been brand new and sealed.