Thanks for the replies guys
Firstly, I don't believe that good golf course design means that the course needs to look natural. Take a look at Sean A's threads on Kington Golf Club which has modelling that is most obviously man made but looks right. For that matter any bunker on an inland course (with very few exceptions) is an obvious man made feature but this does not stop many people enthusing about it. Even on links courses the bunkering is often very obviously artificial with its sod walls.
I think the drainage issue is probably the biggest problem though flat does not mean completely level. What has always suprised me is that the main drainage on courses are not set at 4 to 6 feet of depth. Most drainage at course is set in the first couple of feet when really it would be better laid much deeper as this would drain the general ground and not just the very top surface. On a flat site the use of deep drainage ditchs is something that used to be used in the past but are very rarely seen these days.
I do believe that it should be possible to work with a flat piece of land and produce a great course without moving vast amounts of soil. Even placing a small mound in front of the green such as that on the 4th green TOC and the clever placing of bunkers or ridges around the green can make for a very challenging holes. I do think that width (wide fairways) is very important on a flat course.
Lastly, I find that it is the options and the challenges created by those options that make for a good design. The focus should be more on the substance of the course and not so much the look or surrounds.