Poor ZoTTD. His masterpiece been pulled off from the Android Market without a full details from Google. Peoples start speculating it's because of the upcoming launch of Xperia Play which still in question that the second PSOne emulator FPSe still available in the market together with other console emulator such as gameboid etc. Here is some quotes from engadget regarding the matters. Please google, you should know that emulator is legal. No copyright being violate by emulator developer. It's their own code and their own hard work doing reverse engineering of the system. We all know reverse engineering is legal practice.

Uh oh, the day has finally come. We just gathered from Joystiq (and confirmed ourselves) that the renowned Android first-gen PlayStation emulator, PSX4Droid, has been pulled from the Market. The reason? Its author, ZodTTD, said Google informed him that it was a matter of "Content Policy violation," however the fact it's taken eight months for Google to take action suggests it might have a little something to do with the imminent launch of the Xperia Play, which will have its own mechanism to power the original PlayStation's games. Another mystery is that it looks like other emulators such as SNesoid (SNES), GameBoid (Game Boy) and, in particular, FPSe (PlayStation) appear to be safe for now, which might suggest that there are other reasons behind this removal; but still, the timing suggests otherwise. On the bright side, we can always rely on third-party app markets.

Update: Here's a super generic statement we just received from Google regarding this matter:

"We remove apps from Android Market that violate our policies."

Source