if you look at the recent ipv4 burn rate of ripe and apnic especially, we run out of v4 space in about three years.
Presumably everyone here has read the recent issue of the Cisco IP Journal which has some data to back up what Randy is saying. http://www.cisco.com/en/US/about/ac123/ac147/archived_issues/ipj_8-3/ipv4.ht...
four years from now, when marissa can't get v4 space from an rir/lir and so gets v6 space, she will not be able to use 99% of the internet because no significant number of v4 end hosts will have bothered to be v6 enabled because there was no perceived market for it.
I don't believe that this will happen. End host operating systems have had IPv6 for several years now. When the IPv4 space is exhausted, the vast majority of end-hosts will be capable of running IPv6 by simply enabling it, or installing an add-on package. Of course this does involve some effort but the magnitude of the effort is similar to patching operating systems after the latest worm/virus outbreak. I'm sure that there will be a frantic scramble, but I don't expect it to last long enough for an IPv4 black market to form. Also, I would hope that the RIRs have a formal procedure in place by this time so that IPv4 addresses can be returned and recycled. --Michael Dillon