People like David Choi, Marie Digby, Mia Rose, Sam Hart - they are mostly singer-songwriters, who climbed to fame by posting videos of them singing covers. You'll be surprised at the number of hits they've reached on their posts (over a few million hits!)
And I too, have some friends who hit fame on youtube, with over a few thousand hits for some of their videos, but hey, it's a start!).
Some sing cover songs:
Some respond with the same cover song:
Others write original song, with crazy lyrics:
Maybe I'll do one up myself soon... as soon as I can get over how to look into the camera and sing.
Will you be waiting in anticipation? What song would you want me to sing? =P
But in the meantime, I'll sign off with a favourite song of mine which I chanced upon on youtube - Sungha Jung, a child prodigy on guitar playing "Moon River"