Indeed a 17 year old can and should file a return when income is above the filing requirement or to get a refund of taxes withheld when there is not any tax due.
Whether or not the minor can be claimed as a dependent does not change the fact that they may need or want to file a return.
Most 17 year olds that only work part time likely would be able to be claimed as a dependent.
Please note that the question is not if someone did claim him; but whether someone could claim him. See http://www.irs.gov/publications/p929/ar02.html#d0e1924
See Publication 929 (2007), Tax Rules for Children and Dependents for more complete information.
I hope this helps to understand that a 17 year old can (and often should) file an income tax return.