Ben Goldacre criticises the media coverage of a high profile suicide case, on the grounds that such coverage tends to lead to a spike in the number of suicides* . Similarly after a high profile spree killing there tends to be a few similar events that follow. The almost pornographic focus on that German killer recently is an example of the kind of coverage that shouldn't happen.
In other words humans are influenced by what we see or hear about, this includes fictional depictions as well as news coverage. Sure only a very small proportion of people will be pushed into suicide or spree killings by what they see, but the nature of the mass media is that it reaches a large number of people- and a small proportion of a huge number can be quite significant. Less extreme behaviours might be easier to prod people towards.
It therefore seems likely that the depiction of various kinds of negative behaviour in the media will make them more widespread, particularly if it is in a glamorous form. This is a problem if one believes in free speech or enjoys entertainment that features undesirable behaviour, a solution can't be imposed without violating free speech. Naming and shaming the outlets which do revel in horror stories rather than simply report them is probably the only thing that can be done.
* Conversely suicides decline after blanket coverage of a terrorist attack, so if any terrorists do want to kill a bunch of people, but are feeling kind of guilty about the prospect then do so after a high profile suicide and you'll probably save lives.
update: Just to emphasise- this isn't a call to restrict free speech, just a recognition that for all its benefits it has costs too.