It certainly boosts publicity, but most of the people I know of who have signed up for cryonics are either various sorts of transhumanists or celebrities. The celebrities generally seem to do it for publicity or as a status symbol. From the reactions I've gotten telling people about cryonics, I feel it has been mostly a negative social impact. I say this not because people I meet are creeped out by cryonics, but because they specifically mention various celebrities. I think if more scientists or doctors (basically, experts) opted for cryonics it might add credibility. I can only assume that lack of customers for companies like Alcor decreases the chance of surviving cryonics.