No one is privy to an exact number of average daily MRers. However, considering the number of folks that travel on UA/UA partner flights worldwide each and every day, I would certainly think that the number does significantly exceed your low ball estimate of "100".

"Stealing upgrades"? Wow. Those who are fortunate to be more flexible with their availability to travel can and do take advantage of booking lower fares on UA, that I might add are published and equally available to everyone. Thus, those that routinely book these less expensive fares (i.e., the $5K 1Ks so often complained about) are not "gaming" the system, any more than are the extremely fortunate FTers that have most/all of their travel paid for by their employer, without having to resort to any out-of-pocket spending.

For those business flyers that are apparently unhappy about upgrades being "stolen" from them, do wish you once might invest the hours upon hours of time required to fly the (now) 120 flights for 1K, and make the dozens upon dozens of required connections, all while doing so on your own dime, as a number of us 1Ks do. We buy valid fares, and meet status requirements. We, too, "earn" our status and benefits. Time to quit calling the kettle black.