yeah you can petition to have that limit lifted but following over 2000 people is really taxing on their system, so unless you have that many people following you you would have a hard time getting htem to lift it
Following 2000 on Twitter is sufficient for now, but i believe that Twitter lovers could quickly reach that point...not so easy....
There are people with more than some million followers, not just some tenthousands. Simple reason why you cannot add more: you have added too many too fast and do not have the organic response to it = people following you back. You are on probation now and can only follow 2000+10% more of who are following you now. Usually that number is achieved by removing everybody who is not following you back (let's say -500), follow new people and redo that over and over again - this will get your account suspended now as well, as this is not organic behaviour but spam. Adding people too quickly, even if you stay way below the number 2000 will also get you suspended. Usually it comes quickly from the fact that you do not have a real twitter profil, but one for profit, and the people you follow will block you in droves. To follow more people, do unfollow the ones you do not want to follow any more, but do that gently and not in masses.
The problem comes up if you have 180+ more friends than followers, once you get to 2000 friends. That is when they prevent you from adding new friends until your followers catch up. The key is to go back into the list of people you are following and delete that spam accounts you may have followed and the others who are outside of your interests. If you don't know how to easily do this, then google twitter karma. It is a good, but slow tool to do this. Then go back and follow more folks that match your purposes. Good luck