is it ok to not complete quests in fallout? can the game still be won? for instance, in junktown, i intervened in the assassination attempt on killian, then accepted a quest to plant a bug on gizmo and gain evidence of his complicity -- when i got in his office i was unsuccessful in planting the bug (tried to use it on him and the desk, but only after talking to him -- possibly a mistake) and he basically told me to fuck off. i wasn't in gunplay mode this go-round, so i explored the town a bit more (got grenades from the hospital), then bailed from the town entirely, taking with me the bug and recorder.
another time, i agreed to find out who was raiding the fargo caravans, then got sidetracked and neglected to act on that agreement (i believe i was hired). does ignoring these quests reflect negatively in the game as it unfolds? (has anyone had success with the crimson caravan quest?)
(the only productive thing i've ever negotiated in hubtown was acquiring the holodisk from the librarian -- i sweettalked her into a discount, and bartered for some stimpacs and ammo.)

Nothing that will prevent you from progressing more through the game.
Most quests are not compulsory. You will just miss a little less XP for not completing them.

Some quests untouched may lead to different endings to the game. If you want a given town to do very well or very poorly, you might try to work out what quests (or assassinations :D ) will affect that.
Thankfully, there's lots of endings for the various places, so you have many options on replay.