encoding, is there an issue with quality degradeation if you "encode" a video several times. I assume when you make an adjustment/edit to a video it needs to be "re-encoded" even if the adjustment is small?
Strictly speaking, yes, but if you are re encoding to exactly the same file format / codec the loss will probably be barely noticeable, and if you use "Smart Render" then only the clips in your movie that were altered will be re encoded.
If you have only trimmed the ends of clips then you can use "Smart Copy" and none of it will re encode. You may find though the the cuts may be a frame or two inacurate after the Smart Copy.
I'd say none -- if you mean re-encoding from the original material. Losses are probably inevitable, though perhaps not always noticeable as Ss says, when you are encoding something that has already been encoded. eg: AVCHD camera material >> encode to mpeg2 for a DVD >> re-encode from mpeg2 to mpeg4 for a mobile device.