[monocasa]

* ANDF/TenDRA - Never really used except for research purposes, ie. no critical mass.

* JVM - Most heavily used implementation borked the sandboxing. It also forces a GC down your throat, which is great for 95% of use cases, but the other 5% are really important too.

* NaCl - Really cool, but ultimately reliant on weird CPU features for protection. PNaCl was trying to fit a square peg into a round hole with the whole trying to make LLVM IR platform independent thing. WebAsm took a lot of ideas from these projects (and asm.js).

* P-Code - Really cool, but ultimately probably a victim of it's time. A little simplistic for modern architectures as it has no real concept of a memory model or atomic primitives.

* TIMI - Unbelievably proprietary. Even if you were to document it well enough to build an implementation, IBM would almost certainly sue you into oblivion.