Spam Inc – the new buying frenzy

Two months ago Symantec bought anti-spam vendor Brightmail for $370 million. Today Cnet is reporting that it bought anti-spam vendor TurnTide. It’s obvious that the issue of spam is a HUGE problem, but I wonder if there really is any solution – other than challenge response systems?
Cnet reported further that TurnTide goes a step further with its Anti-Spam Router, a hardware and software package. Working at the edge of the network, or the point at which a corporate network connects to the Internet, the antispam router looks at the actual packets of information in messages and determines which ones are likely to have come from a spammer. Using features inherent in the TCP/IP, it can limit the amount of traffic being sent from these sources.