My personal thoughts are there is no reason to limit pool workers, there are too many easy ways to get around it. However, I'd say the solution is to show only their first 5 in the logs and then a note that says "57 additional: 542246 (584455)" Ultimately even big miners are a benefit to the pools. The way I see it, a big farm would just as well be off solo mining, they'll gain the law of averages and not have the overhead of pool communication (which is very small, but in aggregate adds up).
With a miner with a lot of hashing power though, you need to watch out for the risk of a 51% attack or the possibility of one.
True, but do take into account we have a lot of hidden miners that arent in the pool, I dont know why but we have had about 300-400 solo miners since the beginning. I am just making this assumption based on blocks not solved by the pool and the connection count to the node.biblepay.org.
Right now, since we're still in CPU only mode (and it seems mid range CPU's are punching out of their weight class), it would take a pretty big miner to go 51% (whereas if we were ASIC, well, one guy with 25 idle Antminers could fork the system and own us all). The other beauty is right now, you can call up 5 of your friends that have a PC but only surf or play light games on it (casual computer users), tell them how to mine this coin with little impact on their system and they'll be offsetting any big farm due to the mid-range CPU bias right now. Basically, my mom could mine this coin. Since she's got an i5 processor (if I remember correctly), she'd offset approximately .5% of a 100 worker farm. Multiply that by all our parents, vaguely computer literate friends and coworkers and a 51% attack in the mining sector becomes a tough feat.
I would be curious to see just how many solo miners there are, I've got a couple boxes solo just for the experience and I'm a fan of the law of averages (and believe there has got to be SOME sort of overhead to being in the pool, which for most users is so minor that it can be safely ignored, but for someone throwing 1MhS at it, probably starts to see a better return solo after a few months).