I tend to take the lane early, too, if there's empty space, especially on my morning commute. I have one left turn with no light, where there's a lot of traffic going the other way and not a lot behind me. Wednesday I saw a big truck pretty far behind me so I got out and took the lane and clearly signaled because there were no oncoming cars for once. The truck should have slowed a bit more to pass me on the right; he came pretty close, but I knew he saw me. I feel safer taking the lane earlier, too. I think the experience you had reminds us that some motorists just don't realize that cyclists need to act the same way as motorists. Would he have passed another car on the left, if the car was signaling?