According to GoNintendo and Wikipedia, Super Turrican (but not ST2 or Mega Turrican) was removed yesterday, March 7th.
I just called Nintendo (because I'm pretty upset, as I planned on buying it this(!) weekend), and they said that they had no internal data on the removal. They said it could simply be a "lapse" where the game is unavailable for whatever reason for a short time. But they had no idea beyond that.
Would anyone care to check and see for themselves (and post back)? I won't have access to my Wii for a while still.
Edit: Forgot to say, I'm in the U.S. Please post what region you're in too 