most of the time, the best trade is no trade. and i definitely understand full-time trader myopia. the power not to participate is actually a pretty potent one (imo), especially for people who provide liquidity on any scale, day in, day out.
Roubini has been recommending to go short since 2006, do you think anyone could have made money shorting 2006? Not to mention 2007.
I'm not a Roubini follower, but perhaps he had longer time frame in mind with his call? He started getting heavy short bias @ 1300+ in 06. If he acted on such as a trader/investor, last I checked he would be up 25% as of today utilizing non-leveraged indices/instruments.