I don't think it's common. Nearly all US tracks are probably anti-clockwise, because of NASCAR. Japan and Australia both have an even mix I think, like Suzuka is anti-clockwise (kinda sorta not really, damn figure of eights

) but Fuji is clockwise.
You know what? I think this is an interesting statistic that I will have to look into.
I'll try and go through the Master Tracklist and find out how many are clockwise vs. anti-clockwise.
Edit: Screw that, taking me ages. I got up to Canada and the majority was leaning towards Clockwise.
To sum up:
Japan? Hmm...
Twin Ring Motegi - Clockwise for the road course, Anti for the Oval
Suzuka - Clockwise
Fuji - Clockwise
Tsukuba - Clockwise
Okayama - Clockwise
Sportsland SUGO - Clockwise
Autopolis - Clockwise
I see that Japan is in fact Clockwise.
Lets see about America:
Laguna Seca - Anti Clockwise
Infineon - Clockwise
Watkins Glen - Clockwise
Indianapolis GP Road course - Clockwise
Daytona Road Course - Anti-Clockwise
Detroit Street Circuit - Anti-Clockwise
Detroit Indy Grand Prix - Clockwise
..and so on, here it seems there is a balanced amount of Clockwise vs. Anti courses, but thats not counting Ovals...which there are several hundred

and they nearly all seem to be Anti-Clockwise (but one of the many Americans can correct me on that).
Australia, heh, lets see then:
Melbourne GP - Clockwise
Adelaide Street Circuit - Clockwise
Mount Panorama - Anti Clockwise
Queensland Raceway - Clockwise
Lakeside Park - Clockwise
Amaroo Park - Clockwise
Eastern Creek Raceway - Anti-Clockwise
Hidden Valley Raceway - Anti-Clockwise
Lowood circuit - Clockwise
Morgan Park Raceway - Clockwise
Surfers Paradise Street - Anti-Clockwise
Phillip Island Grand Prix - Anti-Clockwise
Sandown Raceway - Anti-Clockwise
Symmons Plains Raceway - Anti-Clockwise
Aussie: Clockwise: 7, Anti: 7. So once again, equal amounts, though I'm guessing that 20 or so I couldn't check are Anti-Clockwise, so Australia seems to be predominately Anti-Clockwise like America.
These were all of the circuits I could find with maps on wikipedia that told me which direction they are generally raced, so its only a rough guide. But its enough for me to be able to say that in my opinion,
worldwide the majority of circuits seem to be run clockwise.