To me, that pressure is the biggest problem in terms of relying on voluntary restraints. Those who do accept voluntary restraints find themselves at a competitive disadvantage because another news group out there will take advantage of their restraint. It really affects the level of public discourse. Look at the conflict in the broadcast media over whether to break away from the coverage of the O.J. Simpson civil trial verdict to air the president's State of the Union message. When you have reporters being rewarded for things that really don't serve the common good, there's need for reevaluation by society, falling especially on the offending profession.
Journalists have an obligation here.
The public good may be served by entertainment, but some things should not be seen that way. Trials don't qualify as entertainment. Our system should be elevating the process. But a lot of criticism of journalists should be directed at the public. Basically, we get the media we deserve.