Amazon stores would sell Fire products, act as pickup/drop-off locations.
With 4,000 stores in the U.S., RadioShack has an established retail presence (even if it's failing) that could be rapidly re-purposed by the right buyer. Amazon has shown an eagerness to expand into brick-and-mortar retail in the past, hence the buyout talks. It's unclear if Amazon would buy all 4,000 locations.
If the deal were to go through, Amazon would use these new locations to showcase the growing range of Amazon products. Fire tablets, phones, and streaming devices, the Kindle line of eReaders, and a selection of Amazon-branded accessories (HDMI cables and the like) would be on display. The stores could also act has a shipping hub for online purchases, allowing eCustomers to pick up purchases, or drop off returns. Additionally, same-day delivery via the Amazon website could also operate out of select locations.
Also in the buyout mix? Sprint, which is said to be interested in up to 2,000 of RadioShack's locations, and Brookstone, a chain typically relegated to shopping malls.
RadioShack is on the verge of bankruptcy, and is going to be delisted from the New York Stock Exchange after defaulting on a $500 million loan. As the end is seemingly nigh, an asset firesale could help repay the defaulted loan, and settle some or all outstanding debts.