This is the same debate that was going on among Cable TV vs. Tivo a few years back. With Tivo, you're able to skip the commercials and so Cable TV got mad because their advertisers were getting short changed and revenue would fall. Advertising is just a way of life, it pays for your television programs and it should pay for the content you frequent online as well, imo.
it is a bad news for us ,if there are more and more people use it ,how can we earn money from google adsense?
I don't think the news is all that bad. Most people won't take the time to download Firefox. Then even if they do, most won't take the time do install any Extensions. If this was built into Firefox, I'd have to agree with you. Having said that, this FF extension is great. With that extension and the Filterset.G Updater extension (which downloads ad filters automatically), I never see ads on any site except my own. I've added my site to the whitelist so I can monitor how effective ads are and to catch reall off-topic ads. I'm also a firm believer in Tivo and can't remember the last time I watched commercials on a TV show. I've found that the best shows are able to incorporate the commercials right into the show in a way that isn't obtrusive. That's the future of advertising.
I have 40,000 uniques/month... only 25% of them use FireFox... of which I'm sure less than 10% have AdBlock... So I don't think it's an issue...