Before profile pictures, there were bumper stickers. You could load your car up with "Good Planets Are Hard to Find" or "I Believe in the Second Ammendment to Protect the Other 26," and everywhere you went, people would know something about your beliefs. The difference, though, is that cars have a lot of bumper sticker real estate. You don't have to choose just one message, and the ones you do choose are out there for years at a time.
Profile pictures are sort of about beliefs, but they're more about presenting a carefully crafted public image. A rainbow mat is all right for awhile, but eventually you're going to want to feature your new girlfriend or impressive rock climbing skills. As one Slate colleague said, it's "such an existential crisis." So if you used Facebook's Pride filter to show your support for same-sex marriage after the Supreme Court decision, when and how should you take it down?
If you participated in other Facebook profile picture trends, like Kony 2012 or the red equal sign (another marriage equality campaign), you might be familiar with brute force approach: that is to say changing your picture whenever you frickin' want and not worrying about it. It's a totally valid position. You supported the movement at its peak, there's proof of your support in your profile picture album, time to move on.
Alternatively you might have adopted the one-day tack. You show your support for a day, but then decisively return to your old picture (or add a new one) as a way of making the statement while still setting boundaries. No awkward trail-off, no switching at 3 a.m. so your friends don't see.
But if you're a little more neurotic (or just thoughtful!), you might worry about what it means and what message you send when you switch from showing support for and spreading awareness of a major social movement to repping your face on a particularly good hair day.
My personal approach is not to adopt advocacy profile pictures in the first place. My beliefs are constant, and I don't hold them to be socially acceptable. The downside to this is that I'm missing an opportunity to publicly stand in solidarity with causes I support, and I'm potentially stopping discourse with those who disagree with me before it can even start. All of that just so I don't have to decide when to remove a profile picture?
The best we can do is probably just to be deliberate about decisions to post or not post a rainbow profile picture and then eventually take it down. Social media and activism have a shared goal of engagement, so it's only fair to give as much thought to a political statement as we do to an image of ourselves (even if we don't like to admit that any thought went into the latter at all).
Advocacy trends on Facebook, their rise and especially their fall, tend to have a particular trajectory that's already been identified in grass-roots organizing. For example, in reflecting on his work during the Greensboro, North Carolina, sit-ins in 1960, Franklin McCain said:
What people won’t talk (about), what people don’t like to remember is that the success of that movement in Greensboro is probably attributed to no more than eight or 10 people. I can say this: when the television cameras stopped rolling, the folk left. I mean, there were just a very faithful few. [Joseph] McNeil and I can’t count the nights and evenings that we literally cried because we couldn’t get people to help us staff a picket line.
Showing up for television cameras is certainly better than nothing, but it doesn't form the core of a movement. And every profile picture that goes up will someday come down. Probably the next time you go on vacation.