Fairly obvious but true, good B2B companies usually have strong balance sheets and often minimal debt. The Internet appears to be B2C from a users perspective but fundamentally, the business models i.e advertising, commission, are basically B2B. (Google Adwords, eBay Stores)
I'm working on a B2B startup if anyone's interested in discussing or exchanging ideas. Traditional B2B businesses (non consuming facing) are largely lagging in terms of the transition to the Internet meaning there's definitely opportunities.
I've recently dipped my tail into writing Android applications, and I've been shocked at how my existing (business) clients jumped on them. Now I'm developing a web app / mobile app combination to see if I can generalize it.
I feel that by comparison B2C mobile apps are infinitely more risky (if more scalable), and don't really understand why everybody is so set on them...
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.
I'm working on a B2B startup if anyone's interested in discussing or exchanging ideas. Traditional B2B businesses (non consuming facing) are largely lagging in terms of the transition to the Internet meaning there's definitely opportunities.