It really just depends on what your friend of a friend wants to get out of riding - if he's looking to just have fun (and is reasonably fit), there is nothing wrong with getting a 6"+ travel bike especially considering how good the designs are today, but he should be aware of the other baggage that generally comes with longer suspension designs -
1. Heavier weight
2. Higher bottom brackets (higher center of gravity, can be a little less stable on slow stuff)
3. Slacker headtube angles - slower steering, harder to keep down on climbs, more stable at speed
4. Slacker seattube angles - more weight in the back, not as good of climber (can feel like you are pedaling a recumbent)
5. Expensive components - to do a longer travel bike right, the stuff is more expensive (or it is ridiculously heavy or a poor performer) - if I was building up 6" travel bike, you'd want a Fox 36 or a Lyrik on it and those forks are $$$, and then you'd need a strong wheelset, more capable brakes, etc...
If you are fit enough, you can really do any of the local climbs on a 6"+ travel bike, though it wouldn't be as much fun...but then again, who really has fun on the climbs