I don't the darker content at all. (Within reason, of course.) Recently I have started gravitating toward it. But I am picky about who I write it with. At this time, I keep it to my closest and longest writing partners. We know what lines can be crossed and which shouldn't.
I think it depends on the type of site, honestly. For my animal sites, I absolutely do not allow animal intimacy, but for human sites, it's allowed. Otherwise, boundaries are healthy to have, even with ratings.
I writer darker content, mainly because I often write antagonistic characters and my vampires are the type that see people as food. But I do balance it out with my comedy light hearted plots and characters.
I don't mind darker content. However, on my forum, I have a general rating of 2/1/2. However, people can override that rating in specific games (that reminds me, I should probably explicitly.. state that ... somewhere...) that aren't necessarily visible to Guests.