danaoshee posted an interesting comment; speculation is rampant that Harry's scar is one of Voldemort's Horacruxes.
That would explain why Voldemort doesn't want anybody to kill Potter.
I doubt it, though.
Voldemort was ready to sacrifice Harry in Goblet of Fire to bring himself back to life, and I don't think it was a chunk of his soul that was going to do the job.
If Harry was carrying a chunk of Voldemort's soul in his scar, the Inferi in the cave would have probably ignored him completely; the odds of them not being commanded to allow Voldemort access are pretty slim.
The killer, though, is that Harry's scar is his connection to Voldemort. Voldemort doesn't have connections to his bits-o-soul. He didn't know that Tom Riddle's Diary was destroyed until he was told. He probably didn't know that years ago Slytherin's locket had been replaced with a fake. It doesn't make sense that Harry's connection to Voldemort would be because his scar was a Horacrux.