Android's first N64 emulator, N64oid, developed by the Android emulator man himself, Yongzh has been removed for the Android Market. If you have been wondering where it is, if Google took it down or when it will be back, why it was taken down, there are answers for those questions. It is only temporarily off the Android Market.
N64oid was not taken off the Android Market by Google but instead by Yongzh himself. Why would he do this? According to the developer, he has taken it down for a couple months to work on it. This was spurred on from some complaints on the Android Market from people complaining that it wasn't up to par and leaving bad ratings. The Android Market can be a rough place when it comes to user feedback and because developers still do not have any reasonable way to respond to comments, we are left at the mercy of the population.
When it comes to emulators, a lot of people think that every game for that system it is emulating should work perfectly. Unfortunately this is not the way when it comes to emulators. Every game won't run perfectly simply because it is an emulator and not the native system. There will always be a game here and there that just won't function properly but for the most part, most games will. There will always be bugs when it comes to emulators, especially when trying to get it to run on so many different Android devices. So yes, a few bad apples have hindered it for everyone.
It is alright though, it will come back to the Android Market, we will just have to wait a couple of months after Yongzh has worked on it more. Until then, if you were one of the lucky ones to get N64oid before it was pulled off the Android Market back in mid-March, you can still use it, just don't expect any updates for the next little while.
Update April 12th, 2011 9:58am: To answer the inevitable question about having to repurchase it if you already own N64oid, no you will not have to repurchase it if you already own it when the new version is released.
Developer Website: N/A
Website Referenced: Android Forums