What most frightens a business or consumer user? Being left without support when Murphy's Law comes calling.
The last few months have seen a whole pack of Murphys come through my life. Every computer in the place has gone on the fritz. My iPod suddenly crashed.
But the only time I really got scared was when Open Office started losing files. That's because I didn't know what to do about it. (Still don't.) The program's support system and documentation are poor. Sure it's free -- my son has a version in Arabic and one of his teachers has a version in Chinese -- but when you have trouble you are on your own.
In contrast to free software, open source has a business model, payment for support. This is why businesses are no longer afraid of it. When you can get the attention of the guy (or gal) who wrote the thing, that's value for money.
The problem remains one of scaling. As a user base grows, you have to build a support process. That takes money. More frightening still, it takes bureaucracy, to prioritize support calls and follow-up.
If open source can't find a way to build such structures, and get paid for them by users, then open source will fail.
And that's the scariest fact of them all.