A useful point of comparison here is a part-per-million chance Looking at the other actions which cost a micromort, I'd say that if the odds were worse than a part per million, filling out the sign-up paperwork alone would outweigh the benefit. (My personal best guess is that the odds are closer to 1%, which, for me, is close to the break even point, mostly due to the financial part of the costs.)
From Mike Darwn's Chronopause, an essay titled "Would You Like Another Plate of This?", discussing people's attitudes to life:
Conclusion, graphs, and references in article. As usual, I recommend reading Chronopause.com as Darwin has many good articles; to quickly link a few: