How many keywords...?

So I've been doing this IM stuff for a year and a half and I'd say I have a realllllllly good understanding of how everything in the industry works, but I still consider myself a newbie, so I was wondering...Say I have a new niche, and the keyword I'm shooting for is, say, "pink bunny rabbits". I registered pinkbunnyrabbits.com. Now I write an article and submit it to EZA, then Digg it, submit to to Propeller, make a Blogger blog, etc...should I still use that same keyword on each of those sites? Or should I use a different related keyword, (i.e. I have pinkbunnyrabbits.com, then submit an article to EZA using the term "bunny rabbits that are pink", then Digg "pink bunnies", etc)? I used to think that I shouldn't use the same keyword on all of them, as I would be "competing" with myself in the SERPs, but I'm starting to think I SHOULD use just that one keyword, so I can more or less dominate the first couple pages of Google for that keyword, much like you would do with software like SENuke and Brute Force EvoII.

What do you all think or recommend is the way to go?