This is one of the most interesting threads on bitog and I suppose I should thank the OP for being so open as well as whoever got the thread unlocked for allowing it to continue.
My thoughts will start with this quote:
The OP engages in a technically legal business, but ethically dubious. It's a bit odd that there have been so many complaints about the car owner's attempted "extortion". She was behaving no differently than the significant % of people who always try to take advantage of situations to their own financial benefit. The difference between her and the OP is that he is way better at it. She tried to be opportunistic in that situation. He created a premeditated opportunistic business.
The OP offered $2500 without negotiating despite the car being worth half of that and despite him being a skilled negotiator. He did that because to him it was worth doing it to avoid any headaches if she decided to go home and think about it. He offered her that amount because he wanted the problem to go away. If he could have risked offering less, he would have. I don't think he offered the full asking price out of the goodness of his heart. The OP fully understands that there are, like him, opportunistic people out there, and he didn't know quite who he was dealing with.
Should the lady have been happy regardless of finding out her engine had been destroyed? Logically yes. But how she feels about it and asking for more is her prerogative. She may be perfectly happy now that she's calmed down. She may have been upset that she sold her car to someone she trusted but no longer does (some people decide they want to sell their possessions to people they think will look after them or people they like). Or she may have put on her anger to get more money. And really there is not much wrong with that if we apply the ethical standards of many businesses including this technically legal roam towing business.
Lastly, if you google "roam towing", there are some terrible stories out there, including ones where people coming to pick up a vehicle had a previously parked car follow them into the lot, the gate closing immediately, and then being told that now both cars would need to pay $x to be released. So yes, the lady was technically unreasonable after having gotten her asking price, but far more unreasonable things have been done in the technically legal roam towing business.
Originally Posted by ToadU
I actually created the industry of "Roam Towing". It didn't exist until I created the concept. We impound hundreds of cars a week. I only accept cash if you would like your car back. Football game weekends we impound over 1,200 cars in a 3 day period. I have armed security at my tow office and bullet proof glass transaction windows. Learned that lesson the hard way years ago. No one killed fortunately.
Oh, regarding the added links, my advice if in the Gainesville Fla area, be careful where you park. 
