Where did the money go? Lot's of places and in actuality a lot of the money was used for the good. Roads, bridges, infrastructure, education, and on and on. Was any wasted? I'm sure it was. Kind of like the saying "I spent some of my money on wine and women, the rest I just wasted."
Mention was made of the perceived high property tax. One thing that didn't happen was the sharing of much property tax. Property tax is used by the local governments (counties, cities, and schools) that have no other means of income. None, or very little of the oil tax was given out to those local governments for General Fund expenditures. General Fund is what pays for every day operations. Not infrastructure of other special projects. For this local entities expenses went up just like everybody else. The state property tax buy down was generally used for special projects that in some cases the state mandated. Go to the local entity that you think is wasting your tax money and go through their budget and decide what you want to do without. I'm betting the list will be pretty short. You are not allowed to just say "we need to spend less" you must actually decide on "what you would spend less on." Police? Education? Snow Removal? No more Diesel Fuel when your roads are Blocked? It's not as easy as you think.
Someone is correct in the observation that the state is not broke. There is a huge balance in special funds that is only allowed to be used for certain issues. Perhaps that is a good thing that prevents the state from entering a very big hole. Time will tell.
In the long run someone mentioned 40-50 rigs all the time. I agree that the Bakken exploded and we would probably have been better off with a slower growth but it is what it is. No different than any other business. Make money when it's available. When wheat was $15-$20/bushel (short time), there weren't any farmers saying "I don't need the money, I won't plant any wheat this year." The Bakken created a large amount of jobs for our young people. Made it possible for some to move back into the state. The state is not the same but I think we're better off than we were prior to the Bakken.
Did the oil boom bring in problems, absolutely. How we handle those problems defines us as a state.