It looks like RR may not go #1, Owl City already has a lot of DLs for this week and even if Rihanna goes #1 on 'Tunes then Owl City's numbers will be extremely similar. Rihanna is unfortunately probably not going to get a massive lead over Fireflies, and since Fireflies has much more airplay than her and streaming it tips the balance in favour of Fireflies.
I'd LOVE to be wrong though, and see in 4 hours that RR has DOUBLE the pop bars of Fireflies!
