Validate fake iOS 5.1.1 user agents by checking for webp in the Accept header.

No Safari version supports webp at the time of writing.
Whitelist feedly requests for missing Accept header.

User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_7_2) AppleWebKit/535.7 (KHTML, like Gecko) Chrome/16.0.912.77 Safari/535.7 AppEngine-Google; (+http://code.google.com/appengine; appid: s~feedly-social)
Add the default Go client to the blacklist.

User-Agent: Go 1.1 package http
Whitelist the vienna feed reader for OS X.

User-Agent: Mozilla/5.0 Vienna/3.0.0 Safari/537.75.14
Add support for validating Opera Mini requests.
Fix brainfart.
Add a few more headers that should point out the use of a proxy.
Blacklist sistrix crawler

The company links you to a crawler page that seems to imply they want
to be a new search engine, while on the other hand, their main site
shows they are a SEO company. Bad way to play.

User-Agent: Mozilla/5.0 (compatible; SISTRIX Crawler; http://crawler.sistrix.net/)
Whitelist QuiteRSS to send HEAD requests:

User-Agent: Mozilla/5.0 (Windows NT 6.1) AppleWebKit/534.34 (KHTML, like Gecko) QuiteRSS/0.14.3 Safari/534.34
Make sure to stop the new generations of scoutjet too

User-Agent: Mozilla/5.0 (compatible; Blekkobot; ScoutJet; +http://blekko.com/about/blekkobot)
Our friends at topsy tried to go stealth, and new requests look like this:

GET /2014/04/heartbleed-and-xine-project HTTP/1.1
Host: blog.flameeyes.eu
Connection: Keep-Alive
User-Agent: Mozilla/5.0 ()
Accept-Encoding: gzip,deflate

Blacklist their hosts *and* filter out the User-Agent.
Be a little more lenient for NewsBlur still, maybe I should send them a pull request

User-Agent: NewsBlur Feed Finder (Mozilla/5.0 (Macintosh; Intel Mac OS X 10_7_1) AppleWebKit/534.48.3 (KHTML, like Gecko) Version/5.1 Safari/534.48.3)
Make the fake Safari/iOS rule stricter, as not all the spammers limit themselves to 5.1.1.
Use @contains rather than @strmatch for performance reasons.
Validate requests coming from archive.org.
Fix go library detection.
De-blacklist flipboardproxy, but do mark it as a stealth robot.
Blacklist MonitorHTMLcollector, bot that does not use robots.txt
Stop the new wave of comment spammers that POST with image/x-bitmap in their Accept.
Yahoo! Slurp now also uses yahoo.com hostnames.