From a purely materialist perspective, it’s difficult to escape concluding that thoughts are things, with substance of some unidentified sort. From a religious perspective, thoughts directed to our Creator have long been known to be powerful, and that power is magnified by numbers.
The hair-on-the-back-of-your-neck sensation, that knowing you’re being watched feeling, is a different matter. It’s ancient, predator-prey stuff. Ignore it or become divorced from it at your peril. You really can tell, if you’re paying attention.
How? Don’t know.
It's my observation that thoughts have mass and energy, and that they are capable of affecting others at a distance. I've observed the phenomenon too many times in life to deny its reality.
Further, I believe that the aggregate negative thoughts of millions of Americans are affecting Mr. Obama's mental state. There's a LOT of ill will being directed at him on a constant basis, and I'm sure he's perceiving it.
I'd be willing to bet that if every Freeper simultaneously put out a strong mental intention for Obama to resign immediately, we'd see him do that very thing.