People are using an open source browser + Flash Player + PDF Reader.
If you don't trust Google's Flash player and PDF reader, feel free to take them out. In fact, you don't have to, because using Chromium would be equivalent to doing this.
People arent using trademarks, they are using software. And the same is slso true for FF. The open source one is called iceweasel, because the logo and name of Firefox are protected.
A compiled chromium source is identical to Google Chrone, except for the icon and name. Just like with Firefox.
* The Firefox logo is not released under a free license
* The Firefox name and logo are trademarked, and Mozilla has strict policies you must adhere to if you want to use them
However, you can build Firefox without using the name or logo. Requiring derived works to have different branding does not mean a program is not open source or free software.
Chromium is.
People are using Chrome, not Chromium.