In my best Homer Simpson voice- "Ummm... Olive Oil, Argh......"
It seems that I live on protein powder and olive oil. Olive oil is so versatile. Provides good fats at a very reasonable price (especially when compared to flax). Olive oil is mostly mono fats, which means it's not very susceptible to heat. I keep a 3 liter bottle handy at work so I don't worry about refrigeration at all.
As far as science goes (and pay attention all you naturals out there) the body needs saturated or mono fats for the production of test. Now we all know the dangers of getting too much saturated so that leaves good old olive oil to come to the rescue.
Now for word of mouth. When cutting I believe olive oil to actually help in some way toward burning fat. Dogcrapp actually wrote that he believes olive oil to have some kind of uncoupling properties. As far as bulking goes, like it was said- easy calories!
Been a big olive oil fan for over 4 years now. Used to do a high protein, moderate carb, low fat diet. The I got my cholesterol levels checked. LDL was low (good) but so was HDL (bad). Then I started using olive oil as my primary source of fats. HDL jumped to the high end of the scale and has been there ever since (never get tested until orals have a chance to clear the system).
One last note. On my current bulker I get over 100g of olive oil a day.