Yes, social media will continue to cause problems with crowds. While the crowd-forming abilities of social media can be used for good, such as in the case of the Arab Spring protests, it can also cause many problems. Social media has been responsible for enabling "flash mobs" of marauding youths, for example.
In the history of the world, there has not been a faster way for an individual to communicate to millions of people. Social media is a very powerful medium that causes problems with its ability to appeal to emotions and gather large crowds. Until there are regulations in place, these issues will continue.
Social media will continue to cause problems with crowds because of it's very nature of being able to reach unimaginable amounts of people in no time. One can not predict how their posts will spread. Even if something is posted to a limited amount of people, as soon as ONE of those people wishes to share it, it is out of your hands. And with that people will respond and show up to events such as the Mexican city party which will generate more buzz which leads to more people, and so on.
There was one event where a grandmother accidentally invited the wrong person to Thanksgiving dinner. The person accidentally posted the invitation on the Internet, and the grandma was bombarded with additional requests for invitations. Social media makes it easy to exchange information so these things happen. People can share information at the click of a button.