We'll be moving away from MongoDB because it doesn't support certificate validation. What is the point of SSL connections if you don't validate the certificate? It seems that you get all the drawbacks of encryption (overhead, throughput) with none of the benefits (security).
The first is the bug I reported to 10gen about their MongoDB setup. Contained in the bug report is the set of commands I used to reproduce the issue so that you can see it yourself.
The second and third links are about processes in uninterruptible sleep, which is the state my MongoDB processes were in. It should give more detail than I'm about to give.
Linux processes all have a state (running, sleeping, etc). One of those states is "Uninterruptible Sleep". Only the kernel can change a process's state. Uninterruptible sleep ("D" in `top`) is a state in which the process will receive no interrupts (signals). Since the `kill` command is just a glorified signal sender, it ceases to work for those processes.
I'd love to see a solution.