EDIT: My apologies! This article is not accurate, the result of an unfortunate misunderstanding. Chromium will be the default for UNE 10.10 (Ubuntu Netbook Edition), not the standard edition.
It seems Canonical keeps on making changes to their default installation, as has been the case in their latest releases. Empathy replaced Pidgin, GIMP was gone, PiTiVi and Gwibber were included... It appears Firefox is about to become the next casualty in that list.
I personally like Chromium, it is a very fast browser, but if I think about it twice, that's about it. There are still security concerns, a big gap towards natively integrating it into Linux desktop managers, and certain sites just plain do not work with it. In fact, some of those concerns are considered in a BLUEPRINT that has been published on LaunchPad.
I must admit I used Chromium quite intensively some months ago. It pretty much replaced Firefox entirely on my Ubuntu 9.10 machines, as I was a bit bugged with it being slow. However, after some months I started noticing Chromium also had its share of shortcomings. Eventually, when I installed PCLinuxOS 2010, I realised Firefox 3.6.3 was much faster, but just as solid and secure as always. Not long after, I reverted back to Firefox in all my installations. As a side note, I have installed Firefox 3.7pre from Mozilla's development repositories and I have to say it is even quicker.
Long story short, I think Canonical is once again making the wrong turn here. Chromium is still a very young project, not mature enough yet. With Firefox 4 right around the corner, which should close the gap to "modern" browsers in terms of speed and tab process isolation, I find this decision more difficult to justify than ever before.
Firefox will surely remain available in the repositories, so there will be an open door for everyone who, like me, is more comfortable using it. My concern is that Canonical is apparently sacrificing some of its original values, like security and reliability, in favor of the "flavor of the month". I didn't understand the excessive push on social interaction tools and now I don't understand getting rid of an Internet browser which has been their flagship for so long, which is also an industry standard. Do they think popular is better? Hard to tell, but with all the bugs pending fixing, I find it funny that they actually waste a second thinking of replacing the Internet browser.