A business to business marketplace/network, exclusively focused on enterprise/opex. If you think about real world opex e.g office supplies, travel, insurance, a

A business to business marketplace/network, exclusively focused on enterprise/opex. If you think about real world opex e.g office supplies, travel, insurance, advertising, online is the future. The largest marketplaces currently focus on B2C and realistically, there's only two (Amazon, eBay), which explains both the opportunity in B2B and the possibility to build a large company that benefits from network effects. Edit - Technically, eBay is C2C like craigslist, though I'd imagine the majority of their revenues are from B2B, eBay stores. C2C/B2C currently has nearly all the mindshare but as the Internet moves deeper into enterprises this will change. If anything, I'd imagine that the greatest opportunity is B2B, especially when you consider the financial/industrial markets and overall business spend is far larger than consumer goods/services. The problems with B2B are mainly price (negotiation), but also the actual transaction process i.e most businesses operate credit accounts, with varied terms. Get this right and you will have something people want.