The age limit was put in place around a year or so ago, at the time eb had a more mature membership and some posts/topics could of offended younger members. As we didnt want to have to deal with parents complaining about it, we decided to put an age limit on the boards.
We also had a problem with young kids spamming etc, which we didnt want or need. Look at it this way if your under 18 and signed up after the age limit, then you have one strike against you. You know you have lied to us, we know also and therefore any crap will result in you being booted from these boards.