In the past few months, I have seen a number of online community or social communication communities built specifically to communicate messages after death. Some of these sites have very strong presense in the UK. Imagine a Facebook for the dead.

Would you join such a community or pre-make messages so it can be sent after death?

This is one of them:
http://www.futuristk.com

Would I join, probably not. This reminds me of that scenario you see played out occasionally in movies or on tv where someone dies and leaves a video will. It comes across a little creepy to me.