They really aren't. It's about keeping things focused and easy to find things. You have a side view mirror, a starter and power steering pump, all in one ad. What forum do you put the ad in? Exterior parts, mechanical parts or steering & suspension parts? Doesnt matter because no matter where you put the ad it will be partially wrong and will cause confusion. Then the questions in the post will be about all 3 parts making the thread tougher to follow as people read. Then what happens when you sell a part? You can only edit the ad for a week. So then what? Mark the thing sold and start a new ad with the other 2 parts, starting the cycle again.
