As far as I know, there is no 'congestion' on the 800-namespace.
maybe, one of the reasons is that these 'records' have a fixed, 7-digit
length, and 'vanity' numbers have the same length as ugly ones,
spreading the load.
Currently, the 800 space is filling up and they're considering using
another 3 digit area-code (hadn't heard on what they'd finally decided on)
for toll-free calls. The curious thing is that if you have a vanity number
in 800, there's some motivation to get the same vanity number under the new
area code. Doesn't help the {un}clogging of 800 at all... maybe the
IANA would be willing to sell vanity IPv6 addresses :-).
henry