We have had issues in the past with people signing up only to try to sell their items, and that type of membership is more likely to result in someone getting ripped off. The forum requirement of 25 posts and 14 days of registration is a deterrent to curb this activity.
What sections are you locked out of? You should only be prohibited from posting in the Classifieds section and the Open Forum.
You need to be a contributing member ($5) to post in the open forum, which is dedicated to off-topic (non m/c) related topics.