For someone who only wants a camera to take the odd snapshot and never intends to truly "get involved" in photography, perhaps a D100 is overkill. Then again, if that's the case, perhaps any DSLR is overkill. But for beginners who do intend to learn and get involved more and more, IMO, it's a perfect camera ... and now cheap and good enough to keep as a quality second back-up body to any upgrade they may get in the future.
The D100 was Nikon's original entry level DSLR and was therefore purchased by both pros and amateurs. It may not come with fixed macro, landscape, portrait, etc. settings like a basic point and shoot, but it does have a built in pop-up flash and full auto settings. Once a beginner understands the relationship between aperture and shutter speed, along with depth of field and lighting, the "flower", "mountains", and "head-silhouette" settings aren't really needed. Even if they never use the advanced features ( that the D50, D70, and D80 would also have ) ... no harm done.