I also feel that it is rigid to say to not follow more people than #insert a figure#. If I'm interested in multiple topics and there are quite a few people publishing relevant quality content, then why shouldn't I follow 500 people. If I'm OK with not always spotting the most useful posts, but like to be fed with more or less randomly-picked posts that I then decide to focus on - and this is what would happen if each of the 500 people published one article per day and my attention span probably sufficing to scan through 100 posts a day - then why not.
The problem is following people without a solid reason except for the hope that they follow you back to return the "favor". This is indeed something to advice against.