This is true, FB's volume potential is higher than LI. But it is also true that those people who are interested in their "business social network" are accustomed to paying for services that create business value, sometimes paying handsomely. Those people interested in their social network are less accustomed to paying for "social services", and may be less able to put a value on the service (telecommunication services excepted).

It's not clear either that someone couldn't implement a LinkedIn clone on Facebook's API. FB isn't ignoring the corporate space, for example their "networks" feature is tied to a corporate email address anyone who is a member of a company network, you can trust that their identity is real. LinkedIn is even trying to get in on FB's turf, with its status updates.

On the other hand, advertisers tend to want to advertise to the people interested in their "social social network". Advertising to job seekers is inherently limited.

Agreed, but you're less likely to find falsified information on a LinkedIn page. The people on LinkedIn in are more likely to be real. That has considerably more tangible value IMO.

If you mean name, gender and location, then yes, those are less likely to be falsified. Everything else - everything that actually matters such as job titles, job descriptions, recommendations - is just as unreliable.

I personally know many people who lie on their profiles. One of my former startup partners lists herself as a CEO, except we were never structured that way, and she was never the top in command. People inflate their resumes all the time - if they have a one-man consulting company, they are the Lead Architect, if they received options as part of their incentives package, they are a Founder, etc.

Just look at all the recommendations. Literally everyone is Bill Gates and Mother Theresa rolled into one. I have yet to see a recommendation that simply says, hey - this guy is a competent programmer. Everyone is "world-class", "exceptionally talented", etc.

In contrast, none of my friends falsify personal information on Facebook. The incentive simply isn't there.