Never mind the single guy with the, for a VERY short while, hashrate, you should be more concerned with multiple rigs from the same user cheating the system.
Lets look at block 1098 on MaxMiners

Sort by username and go to page 6 and we have

85   HarryPc21 8 0 0.00
111 HarryPc22 8 0 0.00
124 HarryPc25 4 0 0.00
103 HarryPc26 8 0 0.00

If there is a limit of 1 worker per 1 user per pool, how are the pool admins missing these multiple miners???

I haven't checked the other pool but I guess the story will be the same