I agree with everything that was said in the previous answer. However, the question assumes that bullying is a bigger problem than it once was. If we say, for the sake of argument, that bullying is a bigger problem now than it used to be, then we can identify two reasons why this is so.
First, even if the number of instances of bullying have not gone up, bullying is seen as a problem now where it did not used to be seen in that way. This is because we are now much more sensitive to the idea that children should not be bullied and that we should not just expect kids to “toughen up” and take the bullying. Thus, the change is because of what we define as a problem, not because of a change in how often bullying actually happens.
However, it is also possible to argue that instances of bullying have increased. There could be a number of reasons for this. American schools are now typically more diverse places. America is more racially and ethnically diverse. Perhaps even more than that, we are now much more diverse socially. We have promoted individuality so much that people are willing to dress and act very differently. In decades past, there would be fewer people willing to stick their necks out and act differently. Therefore, in the past, there would have been fewer people who would have been seen as good targets for bullying because everyone in a school would more likely have been of the same ethnicity and would have tended to act in very similar ways.
Thus, it may be that bullying has just come to be defined as a problem where it was once defined only as a condition or a fact of life. But it may also be true that our more diverse society has caused a situation where there are many people who are sufficiently different to be seen as potential targets for bullying.
In some notable cases of child suicides linked to bullying, extreme prejudice regarding the victim's sexual orientation was the cause of the bullying, but other bullying factors also lead to child suicides. Jamey Rodemeyer, a 14-year old bisexual student committed suicide following a number of bullying incidents directed against him; Jon Carmichael, a 13-year old who killed himself after being bullied because of his dimunitive size; Alexis Pilkington, a 17-year old girl who committed suicide after being bullied on-line; Tyler Clementi, the Rutgers University student who killed himself after being bullied because of his sexual orientation; and too many others to list here.
The visibility that many of these cases received in the media, especially Tyler Clementi's suicide, helped to focus attention on a problem that has been around forever, although with less-lethal results than occur today. Parents struggling to understand the deaths of their children have become increasingly vocal about the need for school administrators to take a more forceful stance on the issue of bullying.
To the extent that bullying could be considered a bigger problem today is not because there are necessarily more incidences of bullying, but because the internet and social media have made it easier for bullies, especially those who conceal their identities. Before the internet and, especially, before Twitter, Facebook, and other forms of social networking, bullies were physically limited in their reach. Today, within minutes they post intimidating messages and photographs for the entire world to see. The anonymity that the internet provides makes it easier to get away with bullying behavior, while also making it more emotionally destructive for the victims.