Lastly, negotiating in person also has it's drawbacks. Personally I prefer to negotiate by email in most cases. Depending on the other party and your own skills an in person does't always work out the way you would like.I think it totally depends on what you're selling, who you're selling it to, and many other factors.
For example, a guy emailed me one day about a domain I owned, and wanted to know if I'd part with it. None of the domain appraisal tools rated it as having any significant value and I wasn't emotionally invested in it, and had no specific plans for it, so I emailed him back and offered to sell it. He made an offer, I accepted, and told him to Paypal me the money, and then I'd transfer the domain to his GoDaddy account. No "escrow", no face to face meeting, no weird stuff, just email and two strangers trusting each other over $100.00 and a domain. And if F2F had been required, it would never have happened, since I was in NC and he was in Canada. So, totally an appropriate case for doing everything via email.
Now... our startup is in the business of complex, B2B enterprise software solutions which will sell for 10s (if not 100s) of thousands of dollars for a subscription. This stuff will need to integrate with existing legacy systems, and - if successful - will have big implications for the way people get work done. We are not going to get anywhere without some serious face time when it comes to selling this stuff.
Of course, those are two extremes, but I think there are a lot of cases where the higher bandwidth of face to face communication is still very valuable.