It'd take a lot of effort. I wrote an app to exploit over generous early prices myself a few years back and used it for a while but despite the winnings being relatively small I found that one by one the bookies closed or severely restricted my accounts which removed the edge as shopping around was key to getting the required odds. Hence, I can tell you from experience that winning is against the rules so they'll simply refuse the bet. Don't be fooled into thinking that they have to take a bet because that's what they're licensed to do, it's not like the taxi game, they can refuse a client or bet simply because they don't believe they will profit from him or it. Furthermore, I'd say if it's possible it's been done or is being done on Betfair which is owned by Paddpower who would alert the whole trade. There are teams of professionals who exploit the satellite delay by using Betfair's in running markets from the course for real racing, that's probably the most viable methodology for a touch (actually consistent touches) these days. I doubt there's any bookie that'd take more than a few ton on a virtual race regardless of who was offering it.
