The Triumph version of CM7 will only make the carrier name disappear on the lock screen (so will the clock). Currently I think the only way to edit the carrier name is by editing it yourself.
I decompiled the framework-res.apk and edited the eri.xml (located in res/xml/). The specific line is <EriInfo RoamingIndicator="1" IconIndex="1" IconMode="0" EriText="Virgin Mobile" CallPromptId="0" AlertId="0" />
Change "Virgin Mobile" to whatever you like... keep the quotation marks. I just changed it to my name. Save the file, compile the framework, zip it and flash it back on using the recovery menu.
There is a specific way to set up the zip for the flash. I was lazy so I included it into a battery mod zip that I liked by using 7zip to extract it and inserted my framework-res.apk into the system folder. I then re-zipped it, put it on my sdcard, booted into recovery, and "install zip from sdcard"/"choose zip from sdcard". Now my notification screen and lock screen have my name.
http://i376.photobucket.com/albums/oo210/cdtatum08/DSC_1081.jpg
Here is a link to get apkmanager. Just google how to correctly use it. When you compile... framework-res.apk IS a system apk.
Apk Manager 4.9 - Makes Modifying Ur Apk A Breeze (Windows/Linux) - xda-developers
Cheers!