Right, I'm aware of 1) what pump and dump is and 2) the fact that unlisted stocks can still be traded. But the reason the NYSE suspended trading is to prevent pump and dump amidst talks of a buyout with Sprint, Amazon, etc. It's much harder to do so with unlisted stocks...
The NYSE didn't suspend trading to limit the risk of pump and dump directly -- though that's probably among the reasons for their general policies on delisting. The NYSE suspended trading because RadioShack stated that it did not intend to present a business plan identifying how it would return to compliance with NYSE's minimum $50 million market cap requirement for listing. As is policy when that occurs, NYSE suspend trading and began the process for delisting the stock.
