A: Not in a reasonable way, because of the way a jeans waistband is constructed, there is no "split" in the back to take in or let out fabric. Just wear a belt, and or allow them to sag a bit. Jeans feel better with a bit of room anyway.
A2: Railcar Fine Goods does a really impressive job on waist alterations. Their webpage describes the process, which is way more involved than putting in a couple of darts.
This Q&A is taken from the ongoing discussion in our "Ask a Jean" thread. Have a question of your own? Ask it here: http://www.styleforum.net/t/55144/i-have-a-jean-the-ultimate-jean-thread-for-beginners-ask-questions-here