My ratio is oo

Mathematically, Share Ratio (or simply Ratio) is defined as:

Share Ratio = Upload / Download

When Download = 0 in the formula above, the Share Ratio tends to the infinity (in Mathematics, the symbol for the infinity is &infin;, similar to a sideways number eight).

There are three possibilities to get Download = 0:
 * you have never downloaded a torrent
 * all the torrents you downloaded were free (free means that you're not charged with download)
 * you already had the exact contents of the torrents you have, so you didn't download anything, you only seeded them

Example
Your download is zero and your upload is 50 GB. Downloading 100 GB of a non-free torrent (which is an average torrent size in Pleasuredome) will put you in trouble with a ratio of 0.50.

That's why having infinity Share Ratio is OK, but you have to be careful when downloading a non-free torrent because you may be shitlisted much sooner than you expect.

Be careful! Infinity ratio doesn't mean you can download as much as you want. In fact, you also have to get ratio greater than 1.0 on every free torrent you download.