No!!! Initially the score will drop because the new TL, but I've seen that after a month or so the score will increase because his util will be down. If he is responsible with it, new credit is a good thing and will bring the score up over time provided he doesn't max it out.
05/19/08 TU: 703 EQ:717 EX:710
05/08 TU:660 EQ:710 EX:621
04/08 TU:654 EQ:671 EX:618
3/08 TU:608 EQ:624 EX:623
11/07 TU:564 EQ:555 EX: 560
Goal: 700 club by Dec 2008. Can it be done? Heck yeah!! It's done, let's keep it that way!