| Well, that depends largely on whether you consider a net light side shift to not be gaining dark side points. In one convo with Kreia, if you don't go a certain way with a line, you'll lose influence. But depending on how you react to specific items, it will often say "Dark Side Points Gained, Light Side Points Gained, Net Light Side Shift". Ultimately you don't shift to the dark at all, and actually shift light, as the dark points are totally countered (and more) by the light points. If you consider that not shifting dark, then yes, I have done an entire game without a dark side shift. It is fairly simple to do, to be honest.
There are a couple of locations where it is difficult to not shift, though. One is on Dantooine, with the salvagers' claim. The only way to gain at all is to sell their stuff to the lady salvager. Then at least you get something. One would think Zherron would just give you the stuff as payment once he saw they had no next-of-kin and did not will it to anyone else, but no. The other big location is on Dxun, in the Sith temple. If you try to calm the Dark Side Energy in any of the rooms, there is a chance you will fail (depending on their char stats) and shift dark. Characters most likely to succeed appear to be Handmaiden and Visas, and sometimes Bao-Dur. Atton tends to be weak-willed, and I've never gotten Mira to be a Jedi.
One of the reasons the Dark Side path is more difficult is actually realistically correct: most people are at least somewhat "good" and so you gain less points with the populace as a whole by going evil. An evil character survives on his own strength, made stronger by screwing over others. People will give you less stuff, but some of it can be had by killing them.  | 
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