Some couples go in completely the other direction and encourage guests to share as many photos as they can on social media. And Instagram and Facebook mean you get a chance to see all the mad moments at your marriage that you probably missed because you were too busy getting wed. Hashtags for weddings are increasingly popular, but you need to make it memorable and obvious. Check the tag page ahead of time to ensure it has not been used for something else already.
On the day, make sure it's posted up around the wedding, perhaps even include it on the menu or the name cards so everyone has it on hand. Otherwise, you'll be chasing photos 'round the internet and getting interrupted by cute kitten photos until your Silver Wedding Anniversary.