clipped from: www.makeuseof.com 
There are many great advantages to using private torrent trackers. For instance, the reliability and speed of the downloads exceeds those of free trackers, mainly because of the ratio systems. These ratio systems oblige everyone to upload about at least as much as they download.
Ironically, the biggest disadvantages lie also with the ratio system. Don’t get me wrong, I think everyone should upload as much as they can, but sometimes your ratio obligations can put you in some pretty nasty situations.
I remember looking for a certain private tracker invite for a few months. When I finally got in, I tried to get my ratio up as high as possible - stacking up reserves. But however hard I tried, I wasn’t able to reach an approachably decent ratio. There were just too many seeds and too few leeches.