"Anything that inhibits deep rooting, such as a fragipan, excessive stoniness, shallow bedrock, a clay-rich B horizon, a "plow pan". an iron pan, a subsurface horizon of high bulk density, a high water table, or toxicity in lower horizons, makes trees more susceptible to uprooting by impeding root development (especially of vertical roots)...."
Schaetzl, R.J., D.L. Johnson, S.F. Burns, and T.W. Small. Tree uprooting: review of terminology, process, and environmental implications. Can. J. of Forest Resources, 19: 1-11. (1989)
Trees have the genetic capacity for deep rooting, and by deep, I mean all the way to 60 ft. deep for at least one species. Douglas-firs can penetrate sandy loam without obstructions, probably 20 ft., maybe more. Conifers have the reputation for shallow rooting because the ones that tip over were shallow rooted, or because they had been deep rooted, and the soil changed, and pathogens and saprobes were able to convert the roots into food.
Planting a potentially large tree in a soil as described above, or degrading the soil around a large tree, where targets exist nearby, and the wind ever blows, is irresponsible, and there should be liability attached to such actions.

Reply to post by Peter Torres, on November 10, 1998 at 21:34:51:

demonstrable improper planting of any sort should hold some sort of penalty.

but this brings us back to licensing and influancing case law and educating the public.

If all the customer has writen is a a one year contract, and the tree dies five years down the road, what are they going to do?

I was doing a small shrub job in a small town outside of Milw. last month; A crew from one of the biggest local nurseries was sticking a tree in the niebors front yard.

25ft from house to city walk, same from nieghbors drive to front walk.

hole dug four in bigger than ball,

no work done on ball to find crown

excess dirt piled up around base

hardpan clay soil with a chlorotic juniper in the nieghbors front yard.

Whats planted? Sugar Maple I just had to go and say something to those poor people.

jps