While there are attorneys who get jobs at big law and make $150k+ starting, a significant percentage of students entering law school this year will not get a positive return on investment over the course of their career.
{The cost of the law degree} + {The opportunity cost of not working for three years} > {the increased salary that they'll make over the remainder of their career}
EDIT: There were a bunch of articles floating around about this over the past year, here's one: http://www.abanet.org/lsd/legaled/value.pdf, or more recently http://www.nytimes.com/2011/01/09/business/09law.html?src=bu...