I would suggest you make use of tags. FindGameObjectWithTag is a quick operation as far as I know.
I was mainly thinking about developers who want to use HUDText out of the box, or use a modification of the UIFollowTarget. For those with large projects with more than one camera, this simple issue can cause some headaches, which is how I found it in the first place. Another developer was using this line of code in their game which I assume was snipped from UIFollowTarget, but it was causing problems as the wrong camera was being found. I fixed it in my code, but he was asking what would be the best way to handle it in his code for people who just want to use it out of the box without modification.
To be honest, I don't now...which is why I asked. My knowledge of NGUI and Unity is not very good. I figured you could have a solution so that code (even UIFollowTarget that comes with HUDText) could guarantee the correct camera was found in projects with multiple cameras without have to modify it or have the person run into the problem and not know how to fix it or what's causing it in the first place. This is especially true if the person wants to avoid using GameObject.Find().