Sami? No - after the injured and the "injured" players, he was the next best in line. They simply didn't have a choice.
Bosman? Perhaps. But as a power hitter, he can be effective. Sure there's the quota issue, but I guess, yes, he doesn't seem like ODI-class player to me. However, still the best of the quota players. He's still there on merit, albeit within the confines of what's allowed by quota.
Sehwag, though, is in by sheer, blind luck. There are other batsmen who really should be in before him. He has done absolutely nothing to justify his selection - his recent records are abysmal. He's like a Vaughan without the captaincy acumen. He has failed repeatedly after being given a ridiculous number of chances.
Tuffey also comes to mind.
Edit: Sehwag out for a duck as I write this.