Last time I checked, learning to ski on two skis was difficult enough; imagine doubling that. Two legs, four skis? I don't quite get it either, but that's the concept behind these recently-designed Twin Parabolic Skis by Charlie Pyott. To be fair, the concept utilizes four individual ski segments, linked into two actual skis. The segments are connected with hinges and the binding is raised over the gap between the segments.
Wondering why you'd want to try skiing on a completely redesigned concept ski? The use of separate segments allows the skis to be thinned out. According to the designer, "longer and thinner proportions give more speed on hardpack snow". The doubled edges are also designed to aid in maintaining speed when cornering. The two extra edges provide more stable grip, allowing the skier to maintain a higher speed without the need to put the brakes on to check his control. The skis were designed specifically for racers who need to cut every possible millisecond.
Pyott has taken the idea beyond concept and created working prototypes. Don't expect to see these on the Olympic downhill course any time soon, but they do make for a thought-provoking piece of gear. Don't think they'd provide too much float in powder, though.
Sources: Yanko Design via Utah Skier