There's definitely room in the market for several players (in terms of the whole crowd-design/manufacturing space), but I think that down the road, there will be one clear winner. At the end of the day, this industry is a network effects game. Inventors/sellers will always flock to the service with the largest user base to increase their chances of getting their ideas to market. Right now, I'd say the frontrunners are Kickstarter and Quirky, although I've personally seen inventors shy away from Kickstarter because of their increasingly stingy policies. Quirky probably has the most unique model by partnering with big box retailers and tapping into a much broader distribution bottleneck.