I didn't chose to donate this year. Not really sure why. I didn't like the ambivalence of the form. Previous years, if I remember correctly, were set up to where it gave suggestions on how much to donate. Like, .25 cents a paycheck. This year, it didn't. It made me wonder if people would jot down way more than they meant to out of pressure or just not knowing the math well and not taking the time to figure it out. That's not why I chose not to donate, but it did kinda rub me the wrong way to see cases where forms were very informative about your money, and then forms that were less informative.
Anyway, my store only pushes participation, less so on the money earned.