In all seriousness, what do people thinking "praying" will do?

I know this might be a little controversial, but I’m going to put it out there anyways.
This question is regarding the unfortunate events of the Boston Bombing and people’s responses to it on social media. Following the news of this event, I logged into my Facebook only to find several, several posts saying “Praying for Boston right now” or asking people to “pray”. I never understood why people do this. What the hell is praying going to do? The event already happened, no one has any control over it. Could it be that people say this to feel like they’re doing something good for society?
What are your thoughts on people who constantly say things like that? Are you one of those people?