Level separation goes to 2,000 feet above 290 hence the gap then "missing" levels you mention. I guess it was to allow for altimeter errors in older aircraft. All old theory now as much of the world has RVSM airspace now (1,000 foot separation all the way up).
There certainly isn't any VFR traffic at in between levels at those altitudes!
Last edited by Fright Level; 25th June 2009 at 08:41.