Neilsen's PRISM media measurement in jeopardy

The leading media measurement service in the U.S., Neilsen Co. has suffered a major blow as the largest retailer in the U.S., Walmart, declined to go ahead with a comprehensive in-store measurement service called PRISM.

According to a story in MediaDaily News, the complete system -- in which Walmart took part at the beta stage -- was scheduled to be rolled out this year and there were suggestions that this new system might naturally lead to the much-discussed, much-delayed "scan-based trading" system for magazines.

However, with Walmart deciding to go its own way, there are now questions about whether the other players (Kmart, Target, Walgreens etc.) would be sufficient to support the expensive and complicated project.