I became suspicious too, a few months ago. I've decided that people that know a lot more about it than I do, aren't alarmed, so everything must be okay. We know that there are people here who are incredibly good, just because someone is new doesn't mean they can't be really good too.
As for cheating, who knows why people do the things they do? I thought that before the last cheater disappeared he said something about trying to improve his software. That post disappeared along with him, so I can't check to see if I was right.