considering what else could be on a cigar, saliva probably should be the least of your worry. That said I understand your point on etiquette. I would suggest having a back-up "mooch" cutter to avoid any future discomfort.
I have heard several stories of guys wetting a cigar and using the community cutter at the cigar lounge. I always take my cutter with me everywhere I go and rarely loan it out.
While I am with other cigar smokers frequently people ask to share someone's cutter, which is no problem. But, a peeve of mine is when I see a smoker place their cigar in their mouth to wet it before using someones or my cutter for their cigar. I know we are brothers but not that close of a brother, that's just gross not to mention unsanitary.
Hmmmm...never really thought of it till now! I try to keep extra cutters lying around anyways, so it's not an issue here. Plus I'm not sure I really care that much unless the persone is completely gross...In which case I wouldn't be hanging out with anyway's.