Gwen Stefani's "Hollaback" has again fended off all comers to remain the No. 1 single in the United States. For a fourth consecutive week, the cut tops Billboard's Hot 100, as well as the Pop 100 and the Hot Digital Songs charts. A former threat in Ciara's "Oh" featuring Ludacris is starting to fade, but Mariah Carey's "We Belong Together" is picking up steam.
