I think that if you really want to make people think twice about digging then you should put a dollar amount on every outage and sue the construction company for the damage. Maybe this is an unrealistic proposition but I think it is definitely a better solution than putting the equivalent of a land mine around your wire.
I know some telcos do this already. When I worked for GTE (years ago) , we had this construction guy calling into the call-center asking when the "call before you dig" guy would be there. We had no idea (I worked in the billing department at the time), and simply referred him back to the Dig-#.... he called about 10 times in 20 minutes (literally) and finally he said to the last rep "Fuck it, I'm digging..." About 20 minutes later, we started getting "Idiot Overflow"[1] calls looking for the repair department, wanting to report outages, all in the general vicinity of where this guy had been calling from. We called over to repair who said that "I think there's a cable cut somewhere." We were able to tell him immediately where the cut was simply by referencing the backhoe guy's information. :) Repair called us back later to thank us, and to let us know that the construction guy was getting a VERY large bill for the repair costs. Now, if the telco comes out and marks the lines, you dig elsewhere and hit a line, the telco is on their own, which only makes sense. D [1] Idiot Overflow -- when people can't get through to one department, or they don't like the hold time, so they call a completely unrelated department on a different 800 number hoping that somehow we can perform feats of black magic to do what the other department does.