I learned a few years ago from some DEFCON video[0] that someone had figured out a way to do a (basic) port scan of the whole internet in ~1 day (or something like that).
Thing is... it really shouldn't have been that surprising. Although network latency isn't getting that much better year by year (c = c), the amount of data you can process in bulk, correlate, etc. is ever-increasing.
[0] At least, I think that was the conference.
"This program spews out packets very fast. On Windows, or from VMs, it can do 300,000 packets/second. On Linux (no virtualization) it'll do 1.6 million packets-per-second. That's fast enough to melt most networks."
Massscanning the Internet - Defcon 22 (2014)
(I should add that I forgot to mention that IpV6 does make the whole "PortScan the Internet" business a tad more complicated, so that's than argument against me.)