Had a 150 page site scraped (HTML only) 3 to 4 pages per second, by a tool using a unique IP and a unique UA each time; over 50 IP ranges (150 unique IP addresses) and approx 50 different, normal looking spoofed UAs. All Headers looking normal with no identifying characteristics.
Since this did not set off any warnings on my end, it was only caught by a manual log viewing. All participating IP ranges were/are server farms many smaller, unknown to me (now blocked) and at least 2 web-security companies.
Heads-up, no doubt it is coming your way. Wish I could give a better warning. Maybe one of you can find something specific we can block.