Well, they raise awareness and can inflame the people. If one was to shoot them from a gun, they would, in fact, be useless. But oddly enough, that's not what anyone does with hashtags, so maybe they can be useful.
Don't mock hashtags just because you think they're lame. Cyber protest is effective in letting the world know who the real enemy is. And if effective at least then in the real world those with the real weapons will point their guns at the real enemy.
The sooner "cyber-warriors" realize that they really aren't doing anything, the better. All those anonymous marches in Washington, yeah practically no one showed up. Why? Because everyones balls grow 6 times larger on the Internet. We all say things a lot of us would never say in real life. Because of anonymity, once the anonymous threshold is breached and the real world enters no one wants to act.
Everyone here has a good point, 5 point to whatever house you all belong to. :p but, I think this does do something, it helps rais awareness. But those who are aware of the situation need to get up from their electronics and actually do something about it. Now, what that "something" is is hard to tell, because it should be something that doesn't hurt yourself or those around you and doesn't worsen things. I hope no one here gets all high and mighty and starts insulting anyone here who's posted their opinion.
#this means nothing in the real world and does nothing at all.