Youtube videos in 1080p are processed by the GPU via hardware acceleration much like regular movies. So they will have an effect on GPU usage.
I must say, your problem seems rather familiar and I think somebody else here had the same problem. I will admit, I also have the same problem on the same map. I have videos on Youtube which reflect this. Difference being, I run a 5850 at 1920x1200 with all LOW settings, no AA, and HBAO. My little GTX 465 played it on Ultra with no AA just fine no dips. I will get occasional dips of FPS down to 5-19FPS for no reason at all. It'll just bounce back up like nothing happened.
It isn't your CPU. Look at this article here I wrote.
Your CPU and modern games: A guide to those building.
It shows an Athlon X2 6000+ stays at a solid 60fps in BF3 with all Ultra and no AA. So your CPU for sure isn't the bottleneck. I still think you have something running which is causing a hiccup which is why I asked for a screenshot of task manager in the processes tab.
You should also check to make sure Adaptive Vsync isn't enabled in your Nvidia Control Panel.
I should also mention, a simple Google shows you aren't the only one having GPU utilization issues in BF3. As for on the desktop, still unknown.
Edit: More Google shows that the current WHQL driver has a problem with factory overclocked cards causing idle clocks and GPU usage problems. Try using driver cleaner to wipe your current WHQL drivers and try the beta drivers.