Are speculators driving up oil prices?

It is often claimed that speculators are driving up oil prices artificially. That is a possible scenario, yet it wasn't applicable to for example the recent run-up in oil prices. For speculators to drive down oil prices paid by final users they must stock oil in physical inventories, something which they haven't done. Indeed, if you look at the numbers from the Energy Information Administration , it seems that speculation has been holding down prices. Crude oil and gasoline inventories are down by about 5.5% the latest year, while inventories of distillates (like diesel) and propane are down more than 10%.

Last
09/16/11 Week Year
Crude Oil 339.0 -7.3 -19.3
Gasoline 214.1 3.3 -12.0
Distillate 157.6 -0.9 -17.2
Propane 55.359 0.614 -8.361