Bottom line is this: block off your maps, or players are going to get out, no matter what. if you dont want to do it, your maps are flawed. period. thread over.
I am pretty obsessive about keeping players in my maps. This is caused in no small part by the efforts of my friend Scott, who is a veteran map-breaker and always spends a portion of every game trying to get somewhere you're not supposed to. One map I did about a month ago, I thought was close to impossible to escape from - he found a route 5 minutes into our first game. For this reason, the new unlimited budget glitch pleases me greatly.