In my experience, what self-hosted bug-tracking systems might gain in redundancy (a few hours every time a major storm hits) they lose to context switches (which hit team morale, not merely time.)

"Hey, Bob! Can you reset the MySQL server again on the bug-tracking maze set up by Fred over 4 years ago?"

Bob obligingly does so, and then, having been interrupted in the middle of a hard problem, loses his place and can't get back up to speed by the end of day. So while you may gain four hours of butt-in-seat time, you're losing four hours of real productivity on a far more frequent basis.

I'd rather pay Fog Creek to worry about that stuff, and actually ship products.