The usual reason that I know of for a shutter to go as early as this is a (big) impact. A friend had to replace the shutter on a D3 a couple of years ago when it fell out of an ATV... and of course something like that Nikon definitely would tell you it's not under warranty.
However, if there's some other non-abuse reason for the shutter to be busted, it almost certainly would be covered under warranty.
By the way, shutter replacements run about $400, so it's not a truly crushing blow, even if it is something nobody wants to pay. That's more or less independent of model; I had an FM2n shutter cost almost that much many years ago, the D3 above was about $425, and someone else had a different model (D200? not sure) replaced for about $385.
_____ Brian... a bicoastal Nikonian and Team Member
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