What is the effect on my downloads if I stop DHT?

DHT is a decentralized alternative to tracker, it acts as a backup to trackers. When all trackers included in a torrent file stop working, DHT will allow to find peers. With DHT enabled it is possible to download data from a trackerless magnet link or torrent file. You can disable DHT if you use only private torrents (those with a padlock icon). I would keep DHT running all the time.