I have learned the hard way to donate anonymously, if possible. Right after Katrina hit and the losses were being evaluated, I dashed of a pretty generous check to the Salvation Army, and immediately started getting dunned every couple of weeks. I should have paid for a cashier's check and mailed that with no return address. Last year, my wife made a donation to the American Lung Association, and it appears that the people doing the fund-raising sold her name to other groups, because about every week she gets another envelope in the mail containing address stickers, little note-pads, etc, along with pleas for money. At least the Salvation Army did not sell my name to other groups - their regular requests for more money were quite enough.
That's the only place I see people trying to hand out fliers all the time, which is why I walk right past them. I don't think they expect everyone to stop and take one, and there's no communication from them, they just stand there holding fliers out if anyone is willing to take them. Though, there was some obnoxious person dressed up in a chicken suit handing out fliers and getting in the way of everyone on a crowded sidewalk on a day when I was dragging around a heavy suitcase either heading to or from the train station (I can't recall which), and that one I did seriously consider the shoulder check into oncoming traffic option for...I might have wheeled the luggage over their chicken foot inadvertently. 
I don't think I over react...THAT much.