No corporatecoin would ever be accepted by the masses or the media; not even Amazoncoin. After Overstock adopts btc, it is likely other retailers will follow. Another thread could be started on when Ebay/Paypal will accept. Bitcoin takes profit away from them so, actually more unlikely for EBay than Amazon. However, Online Retailers save money by using Bitcoin- - - No 1.5% payment to process creditcard plastic fees. This is big money & this is why online retailers will adopt someday.
Corporatecoins may be used for individual sites as they try cash in on the trend, but I can't see their mass appeal.
Hopefully Overstock's dealings in BTC will be a successful one and more will follow suit. I really think Bitcoins future depends on some big merchants successfully getting behind it.
Ebay/paypal could still utilise Bitcoin, they just need to build it into their system and take a cut automatically. I think ebay should build its own marketplace as there's obviously demand for this.