Basically if you don't know adblock, as the name implies, is a software plugin that you install into various browsers. This plug in allows users to surf the internet and block all ads. So if your page has google adsense on it and a user browses to your page with adblock then those google adsense ads never get displayed. If they don't get displayed then obviously you don't get paid. http://techcrunch.com/2010/11/17/adblock-plus-100-million/
nothing to worry, 100+million adblock download mean that still have more than billions user are not download the adblock
True but 100 million is still a very large amount of users who are basically surfing the web ad free. Also the trend is still growing. So who knows how long until 200+ million people have it etc. I suggest diversifying your revenue streams.
Dont worry about it much. I have seen certain sites which use adblock detect (i dont know how exactly they do it) but if they detect that adblock is enabled they just decline showing the requisite content. That is one really good way.
I would be worry the day adblock comes pre installed with firefox, chrome and ie. Also I'd like to find a script to disallow browsing my sites when adblock is enabled, or if it's not possible, some script that will crash the computer of adblock users.