WASHINGTON -- Despite weak demand in the U.S. and Europe, oil prices climbed this week to near $90 a barrel, and gasoline prices have passed $3 a gallon on the West Coast and parts of the Northeast. Why? If demand is down and supplies are plentiful - and they are - why would prices be going up? Because Wall Street speculators are driving up oil and gasoline prices again - just in time to dampen holiday cheer. "It's all about investor optimism, and that's been the story about 2010. ... That's the primary reason why we're seeing oil prices at...