Now, I'm not saying I'd ever consider buying a department store bike, but anything that gets more mountain bikers introduced to the sport is a good thing to me. A little write-up on a department store Mongoose:
http://reviews.mtbr.com/bike-review-mongoose-xr200
No shame with starting out with a cheap bike, getting hooked, and then upgrading. Anyone remember my green machine!? I think there are some 'first bikes' stories to be had here.