Let's say each block is 200 milliseconds (fifth of a second), then it wouldn't matter if "mom and pop" investors trades show up 1 millisecond past the hour or 198 milliseconds late because you'd:

• trading is queued and done in batches each 200 ms
• this automatically makes it impossible to do spoofing, your order is now live for 200 ms
• better returns for investors due to less value taken by HFT (high frequency traders)
• buy/sell announcements are published at same 200 ms delay
• all market participants have time to react, and send orders inside 200 ms, equally.
• those close to the market get less benefit now
• normal traders aren't having their order queues jumped by their broker

This would eliminate any advantage from low latency network links to the exchange etc, and reduce or eliminate the time window for inside trading - say from stock agents who jump the queue to push up the price after seeing a large order come through - due to a privilege position in the network topology.

Some interesting articles about it: