I healthy argument, I must say this:

I do agree what you said, however I find development standard for Firefox really low and browser performance lower then "advertised" and "screamed to be". I'm not going go to secunia and get a pie chart of total number vulnerabilities that have been reported (which are anyway more than IE + Opera combined). But the number of memory related problems (leaks, overflows) that I’ve seen in Firefox over its development cycle are just too much..

I'm going to say this again you're right about how popularity leads to more problems / weakness being discovered in software but I just find Firefox much less then what it's said to be. It's really no where as secure as thought (advertised) to be. Nor is its performance what it is said (advertised) to have.