Recently, YouTube terminated large channels - Don't let this happen to you by following these steps:
Step 1: Carefully read everything YouTube wrote at: https://support.google.com/youtube/answer/2801973
Step 2: Never use http://www.adf.ly - ever
Step 3: Never put tags into your video description.
Step 4: Always use relevant tags.
Step 5: Never use deceptive titles, descriptions or thumbnails.
It may or may not be. I've read that that's only to shorten links. So maybe it's safe. However, I haven't tried it myself. So I wouldn't know if it leads to Advertisement. If it leads to Ads? then probably won't be a good idea. Try contacting Google.bit.ly is ok right?