Just because there's no in-your-face, obvious, widespread long-term results doesn't mean there weren't any.
For me, this will have long lasting results because people I barely knew or knew but didn't know they supported me rallied to it. Yes, the loud support was only for a day, but the boost to my confidence, the pride in my colleagues, those will last much longer. It reminded me that I'm not as alone as I sometimes feel, that my straight friends do care.
But like Lacey said though, one day won't do much in the long run. It's something that has to happen regularly and often. That's why tomorrow I'm getting everyone moving again to wear white for the stopping bullying thing. Yes, it's not a direct action, but what more can I do? I'm not in the school system, I don't have family in it, and I'm not a resident in this area yet so I can't register to vote and start an appeal. Honestly, what else can I do?
If I can't take direct action, then at least I can still help in this small way.
I see it like this: yesterday was a single raindrop in the lake. No real difference overall. But that one drop of water, if we (as the thundercloud) look at that and go "hey let's get in on that", then each person, each day that stands up for something is another drop of water in that lake. Get enough water over enough time and the dam holding that lake will break down.
Sure, it'd be more effective to just bulldoze the dam down, but when you don't have a bulldozer, grab a bucket, grab up the rain, and start filling it up until it breaks down that way.