There are many similar "crowd funded" things like the ones being discussed here even though the ones here relate specifically to pinball.

When you buy concert tickets IN ADVANCE you are trusting that the concert will actually go ahead and not be cancelled. You might know the band/s playing but have no idea if the concert on the night you have a ticket for will be excellent or crap! You also have no idea if it will rain just enough to make you miserable but not enough to cancel the show.

If the promoter doesn't sell enough tickets IN ADVANCE often they will cancel the show and cite "lack of interest". Yes, I realise we are talking about $100~500 not thousands.

Also many people put down sizable deposits on a new Harley/Ducati/Lotus/Ferrari so they can be the first to get one - this is all very normal business practice.

I guess a lot of the comments in this thread relate to new startups rather than established businesses so there is certainly an element of risk there but if it weren't for risk takers the world would be a pretty dull and backward place IMO.