> as if the only issue with these was that they're poorly coded and supported
A major issue is that arbitrary code can do arbitrary things, up to and including installing rootkits on your machine (for example, the Sony rootkit debacle). The sandbox means it can only do what the sandbox allows it to - in the case of Firefox's sandbox, that's very little.
"I should be able to watch whatever content I want on my system without installing proprietary software, even if that software is highly sandboxed and can't even see anything on my system and can't cause any permanent changes" is a political and moral issue more than a technical one.
A major issue is that arbitrary code can do arbitrary things, up to and including installing rootkits on your machine (for example, the Sony rootkit debacle). The sandbox means it can only do what the sandbox allows it to - in the case of Firefox's sandbox, that's very little.
"I should be able to watch whatever content I want on my system without installing proprietary software, even if that software is highly sandboxed and can't even see anything on my system and can't cause any permanent changes" is a political and moral issue more than a technical one.