Here is what About.com says:

Bottom Line
Based on the studies that implicate the compounds from cedar in allergic and respiratory diseases as well as the impact on liver enzymes, it seems it may well be prudent to avoid cedar shavings as bedding or litter, especially since alternatives are available.

With pine shavings, the problem isn't as clear cut. Pine shavings emit similar volatile compounds as cedar, but the risks aren't clear. It is thought that heat treating pine shavings may reduce the levels of aromatic hydrocarbons that have been implicated as a potential concern, so that products such as kiln dried pine are safe (many pet products are heat treated).

Since the information about the problems is circumstantial and hasn't been evaluated in the context of health problems in exotic pets, I'm hesitant to make firm recommendations. That said, it has been my personal choice to avoid cedar; I have used pine in the past, though recently I have been trying out many of the alternatives available on the market instead.
Here is the link: http://exoticpets.about.com/cs/guine...odshavings.htm

I prefer to keep mine on paper towels. I think it's cheap, fluffy, and comfortable. That way I don't have to go through a whole investigative process to find out if a certain bag of pine is safe. When in doubt, throw it out.