Got every sympathy with anyone who organises anything. It is often a leap of faith, you really don't know who will turn up until shortly before the event, even then poor on the day weather or some other factor can throw a big spanner in the works with a boat load of no shows.
Having to cough up financiallly in advance for stuff is an even bigger leap in to the unknown and there is always a risk that it won't always come off as it were.
The difficult bit these days is as Pete says is getting people to commit before the point of no return is reached.
Clubs as well as individuals are not immune to catching a financial cold on events. If it happens in a club the organisers get hauled over the coals for blowing club funds, for an individual it could leave a very sour taste.
Sometimes you can get round this by coming up with ways of putting stuff on without any financial risk, i.e. tagging on to trackdays organised by commercial TDOs, leaving peeps to their own devices booking accomodation, tagging onto other events, race meets, the European V twin meet etc, but sometimes doing things that way does affect the event in some material way.
I let Pete know ASAP I would be away at the TT for YPVTR, but would do what I could to make sure the DSC Yorkshire region knew it was on, where to get info. etc, etc.
Sure it's frustrating for both organisers and participants, no one wants to see events get canned. IMHO a little understanding of the pressures involved on the organising side helps,
Ray.