I've heard some people say they've gotten banned from following/unfollowing 300/day. I've heard others say that the magic number is 250 a day to fall below twitters limit radar. What are some successful follow/unfollow numbers that you abide by to keep your account from getting banned.
I have also read that massive following and unfollow may result to banning of accounts in twitter. I guess it is much better to do this in certain manner wherein its acceptable . Excessive unfollow and following may look like spam to twitter
I have an account with over 6000+ followers and had no problem at all, I feel you should not keep tweeting links all the time it makes it look like spam.
Read this article from twitter help center - http://support.twitter.com/entries/15364-about-twitter-limits-update-api-dm-and-following
But I think it's better if you check first the profile who follows you and see if he/she is active on twitter before following him/her back
I don't think you have a limit to amount of people to follow or unfollow per day but the amount of tweet for a period of time. You should just follow the amount of people that can follow back and don't tweet links all the time.
I have seen several people follow several hundred people at one time and they didn't get banned but I think you have to be smart about it by not spamming and actually tweeting on a consistent basis.
If you are keeping follow and unfollow on a regular basis, your account would be marked as potential spam. I would recommend you to avoid mass follow or unfollow activity.