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.