The problem with B2B is that it doesn't follow the standard startup model.
In B2C, if you have 10,000 users, VCs will just start to look at you. In B2B, except in some specific instances, if you have 10,000 users you're already a million dollar company.
Thus, in B2C the risk/reward inflection point occurs much later chronologically than in B2B, and for a B2B business, I, personally, think that there is far too much ambiguity before that inflection point.
In B2C, if you have 10,000 users, VCs will just start to look at you. In B2B, except in some specific instances, if you have 10,000 users you're already a million dollar company.
Thus, in B2C the risk/reward inflection point occurs much later chronologically than in B2B, and for a B2B business, I, personally, think that there is far too much ambiguity before that inflection point.