If the score on your hubs gets low enough, the search engines won't pick them up. As you write more hubs and if they are quality hubs with little to no spelling and grammar errors, your hubber score will rise. They very seldom stay low unless your hubs are low quality. Site participation will also help.
I do not believe they will boot you from the site but you may have a problem publishing hubs if they are not quality.
When you reach 100, everyone congratulates you and makes a big thing out of it. It is a big thing. It means that you put a lot of work into getting that big score. No prize, sorry. Not even a box of Cracker Jacks.
The only reason these numbers matter is they show everyone how much work you went to, or not, to get that score.