Some issues with this
@DougS: as a general rule, most providers ignore v4 advertisements smaller than /24, so advertising a /25 wouldn't help much.
Deaggregating doesn't seem much like a scaleable solution either. The whole "our crappy routers are about to run out of route memory if someone adds another 5K routes" is less of an issue these days (if you ignore the Cisco 6509 Sup720 issue from a couple of years back), but there is scope to produce an awful lot of churn as various automated mitigation systems automatically announce new prefixes willy nilly.
The issue is not that BGP is somehow out of date as a protocol, but more that there's no way of signalling trust to peers. SBGP was designed to fix this by allowing people to whether as AS was cryptographically allowed to advertise an IP block, but has never taken off: it's a bit of an all or nothing issue, and the idea of relying on the network to check whether the network is allowed is a tad circular.
Perhaps the ability to signal trust via BGP on a per AS and prefix basis might help: using communities obviously. AS's that have never existed before or prefixes that were previously advertised elsewhere could be assigned lower trust levels, allowing their advertisements to be damped.