definately share ratio is important so that bt survives & doesnt become like other p2p's.Obviously if ur downloading from a public tracker u wont care much about the ratio ,but from a private tracker than u have to maintain the ratio otherwise you might get banned or have to wait for few hrs to download the 0 day torrents.And as we have dynamic ip's sometimes might affect the ratio but if we close the client properly it wont affect the correct ratio is passed to the tracker,