The artist lookup refuses to search unless you enter two or more characters. While you can enter a space to make it do a search, I don't think that's a very intuitive solution.
I can understand not doing the autocomplete search with only one character, but if someone clicks on the search button, they would expect it to search, regardless of the length of the string.
A - http://test.musicbrainz.org/artist/55c6eb6e-8388-497c-acaf-dbff584d0c3a
W - http://test.musicbrainz.org/artist/e0bd0b26-9e80-4813-8e5c-a55ac4552f77