Yet we have had people here advocate jumping off a bridge in front of a trolley if you are fat enough to stop it.

Suppose it could be argued young people create more joy per annum, for themselves and others, than do old people. Suppose (more controversially) that this excess joy over the first thirty years or so of life more than counterbalances the negative joy associated with death (for self and others).

That is, we are assuming that people contribute net positive utility to the world - even when their death after three score and ten is taken into account. Most people would, I believe, assent to this.

Now assume that there is a bound on the total number of people that can be supported comfortably in any milieu. This should be completely obvious given the previous assumption, even in a post-singularity universe. If the milieu is not yet at the carrying capacity, generate more children - don't resurrect more corpsicles!

Given this analysis, a utilitarian seems to have a clear-cut duty not to support cryonics - unless he disagrees that mortal human life is a net plus. And in that case, cryonics should be a lower priority to vasectomy or tubal ligation.

Edit: spelling correction