Good questions! I may answer them at my own journal later - but, on my own writing for a start, I tend to think it's recognisable depending on whether or not I've written whatever POV character I'm using before. There's a fairly hefty amount of 'my voice' in what I write, I think, but I find it really hard to write against the grain of what I see as my characters' style. So I think it's fairly easy to see the links between my Buffyverse fics from Buffy's POV, for example, but I wrote a Faith POV fic for Remix once, which no one recognised as me, and the moment I get out of the Buffyverse and into, say, Shakespeare or Athenian tragedy my voice gets a lot less colloquial and a lot more (hopefully not too) grandiose.

Otherwise, I try very hard to mix up the type of plots I produce, just because I get annoyed when reading people's stories and I realise I've already read them. :D But I have a certain love of anticlimax, which probably gets in more fics than I mean it to. Along with the dragons.