Yes, as I said they are spiders (bots), used to gather web content to be compressed, often reformatted for small screens and sent to their mobile browsers. Those browzzers, Amazon Silk (http://en.wikipedia.org/wiki/Amazon_Silk) and Opera Mini (http://en.wikipedia.org/wiki/Opera_Mini), access the web through their proxy servers, to speed navigation with a more compressed content (respectively SPDY protocol and OBML, Opera Binary Markup Language). Silk, for instance, can't access the web directly but acts splitting content between direct and compressed. Those bots must be recognized as legitimate and needed, not blocked. Blocking them means to shut out some hundreds of millions of mobile users.
Wikipedia bot is different: they periodically check and validate links from Wikipedia pages to external reference sites.
IMHO, you need to whitelist some of their IPs, probably classes of them (I can't guess all IPs they use for bots)
I forgot to tell that these bots blocks only happened since few days, not more than one week.