Plenty of people will sign up.
That won't stop whoever floated the idea from being fired and dragged through the mud. The majority doesn't really care about this sort of thing. A subset of society thinks life is still cheap, or at least no so ungodly expensive that it must be protected at all costs. However, the people who think life is infinity expensive are loud, vocal and their viewpoint is a simple absolute that is easy to defend so the rest of society caters to them.
Edit: And before anyone implies otherwise, I am specifically not passing a value judgement on either side.
Also, I'd go to Mars!
However, risking _other peoples'_ lives (or at least conscious risking of other peoples' lives; the afore-mentioned extreme sports do sometimes incidentally risk other peoples' lives but the perpetrator isn't normally conscious of this) is certainly frowned upon more now than at any previous time in history, especially to no particularly good purpose (as in the link).
Victors get to write history and portray themselves as they desired. Everybody else gets to be the bad guy.
these kind of acts can only happen when life is cheap. ask 10,000 people today to go to mars knowing that at least a few, at most all, will die. i guarantee almost no one will sign up. because we value life now like in no other period in human history. for better or worse.