To give $50 to a charity through Amazon Smile, you'd have to spend $10K. Still pretty nice of Amazon I guess, but if you'd rather not deal with the extra Amazon Smile extensions and junk, most people could just do a $5 or $10 to the EFF and be done.
http://lesswrong.com/lw/lb4/shop_for_charity_how_to_earn_pro...
It's not the EFF, but if you believe in GiveWell, it's a fantastic way to make a sizable (and mostly passive) positive impact.
And the best part: It's stackable with Smile. Presumably, EFF could set the same thing up. (I believe Scott Alexander of SlateStarCodex.com has one set up to support his site as well, so it can't be that hard or restrictive)