Google is a bit like a yoyo at present. We have some very good placements dropping in and out. One morning I can come in and everything is up a few places, the next day its down below where it was then back up the next. I think google maybe playing with algos in real time.
I registered about 20 keyword rich domains about 8 months ago and setup mini sites for them. I did a little mild SEO at the time.
Search terms like <keyword1 keyword2 UK> (Note: keyword 1 & 2 are in the domain names). I am placing well for not very competetive terms - ie #1. But for anything remotely competetive my sites are a no show in the serps.
All of my mini sites deep link into my main site. When searching for keywords in my mini sites I often get the main site retuned instead. So it is having a knock on effect giving me rankings for a second site but not the mini sites that I optimised.