They don't like duplicated content - things like the same tweets and links over and over again. One guy I know has it all on autopilot with Twitter Friend Adder Pro, is adding 500 per day on 10 accounts, is spamming the exact same link again and again and he wonders why his accounts keep getting suspended I have a personal Twitter and a business one, I always make sure I mix my content up, keep it fresh and never follow more than 200 per day on each. Actually, I usually stick to 100 a day.
Thanks for all the useful information, I am new to twitter and found this information to be helpful. Thanks a lot!