Don't know about #1...seems like other player would benefit too much. If the big stack was really gone or disconnected, just share his blinds.

The most extreme case of #2 I can think of happened to me a couple weeks ago. Six players left, top five got a seat in another tournament. One guy went all in for about 2.5x the blind. Everyone else called, everyone checked it down. No reason to bet since placing fifth is as good as first. Gang up on the short stack and bust him out. This happens most of the time I play SNG's, esp. with a bubble boy who goes all in for just a little bit.

ScottieK