It's not censoring #flotilla search - it IS censoring trending topics. A highly selective, possibly first case, of word censoring. It's also censoring #gaza, #israel along with #flotilla.

This sort of selection is apparently based on an operator action/directives rather than automated one (#israil - Turkish for #isreal is not censored).

Now, this is turning highly political and opinionated as Twitter hasn't previously censored #iran or other politically charged words.