One thing I remember from attending the 2006 Nebula Award banquet was a comment from Harlan Ellison, who was the Grand Master for that year. The comment was in the form of a challenge to writers not to play it safe.
For those not in the know, Harlan Ellison edited the two "Dangerous Visions" anthologies. These stories were on the leading edge of the new wave. To read them today, though, is largely to say "so what?" This isn't a knock against Ellison or the dozens of writers with stories in the two anthologies. Instead, it's something of a statement on society.
Things that were dangerous during the new wave, the avant garde, the things people thought but didn't say--well, they're commonplace today.
What is dangerous today?
Openly gay characters? It's been done.
Drug-addicted protagonists? It's been done.
Alcoholic protagonists? It's been done.
Political dystopia after the (liberals/conservatives) rule the world? It's been done.
Pregnant man? It's been done.
What's left? There aren't any taboos left, at least not in American society. I suppose the frontier is the deep dark depths of the writer's mind. That, and unabashed comment on the situation of the day.