Yes. Some people think the original picture released doesn't match Luigi and therefore it can't be the same person, for example.
There's also some people who suspect it probably was him, but believe that illegal means were used to find him and they can't use such evidence in-court because it would require admitting to having a secret mass surveillance network. I assume for such people, a belief in a secret CIA/FBI mass surveillance network came first, so of course they could find the guy using it.