I had the oppotunity to conduct two separate interviews at this year's E3, the first of which was with Obsidian Entertainment co-founder and Fallout: New Vegas senior designer Chris Avellone. The second half of the conversation deals with Alpha Protocol, but here's a bit on FNV skill tags:
GB: We'll obviously be picking our character's skill tags, and I've read that they will have more of an effect on the game than just a skill boost. Can you elaborate on that?
Chris: As with the GOAT test in F3, you'll get a Q&A with Doc Mitchell in Goodsprings at the beginning of the game, and your answers will "suggest" tag skills to take. Like the GOAT test, you don't need to take the suggested skills, you can still choose whatever you want. And you can also re-choose your Tag Skills once you leave Goodsprings if you don't like your choices.
However, we made a conscious effort that (1) every weapon skill had a low level version so you didn't have to wait a long time to get energy weapons, which was a mistake we'd made in previous Fallouts, (2) you can do a lot more with skills you wouldn't expect, notably in conversations. In my opinion, some of the best conversation options you get in the game are Barter ones, when you start using economic arguments to solve quests or convince people of the wisdom of your choices. You should see an almost immediate use for all your skills in Goodsprings and onwards, it was a design mandate.