2 accounts are possible. Back in the days when I didn't fly too much, I had 2 Northwest, 3 TWA, and 2 Delta (because of Pan Am was converted into Delta miles). Of course, everything was consolidated on my initiative.

I can't make any conclusions about fraud because I never tried anything sneaky. I only had multiple accounts because I didn't keep my number handy. Nowadays, I can't help but memorize all my ff numbers (this is sick!)