Major part comes down to is cheating, people using aimers and what ever else to get an advantage.
I use to play yahoo pool all the time when i was a teen. was a blast
That's definitely the biggest concern. There are so few mechanics to online pool, I couldn't imagine it would be very much work at all to make a bot that plays perfectly. Once people start using something like this, the game is effectively ruined. The reason why online pool games nowadays work is because stakes are so low (just playing for fun) that there isn't really much of an incentive to cheat.