I don't have any historical data to work with, but it would be interesting
if someone could break down the total prefix count by length. The recent
slowdown is hardly monumental in nature, and could easily be attributable
to nagging about the rampant and incompetent announcement of /24s.
http://www.telstra.net/ops/bgp has a breakdown by prefix length and the graphs and the data sets are available - look at the base of the page.
Looks like the 1-year view for percentage of total table by prefix length
is broken (well that or the legend is wrong and the percentages have
stayed perfectly flat among all prefix lengths for an entire year which I
tend to doubt).
The data only goes back to August 8 2000 for the prefix breakdowns, but
it's interesting that /24's have increased by 10,000 prefixes within these
last 8 months. The rate of growth is behind that of /20s and /21s, but in
terms of numbers the /24s still make up over 50% of the problem.
I don't think it would be a waste of resources to contact people putting
out large numbers of unaggregated and unnecessary /24s, if anyone feels
the desire to make the net a better place.