The realities of the economy are starting to hit NAC, according to market analysis firm Infonetics.

The firm’s estimate of the market for NAC enforcement appliances has shrunk based on its most recent numbers.

Last year at this time, the firm’s prediction was for $670 million in worldwide revenues for the appliances by 2010. But based on new results, the number has been changed to $534 million by 2011.

That’s a bit surprising given that security is a top priority of businesses, but perhaps not so surprising when you consider two factors. NAC is more of risk mitigation than straightforward security, and it is popular in financial services businesses, which are particularly hard hit by the recession.

“Many NAC vendors found early success selling into the heavily regulated financial services market as well, which has all but imploded, of course, which will have a significant impact on the NAC market,” says Infonetics analyst Jeff Wilson who wrote “NAC Enforcement Appliances.” “The retail sector is being hit hard, too, forcing many retailers to postpone NAC investments.”

These delays in the purchase of NAC appliances may be good for NAC that is built into network infrastructure. The longer businesses postpone NAC purchases, the better cooked the infrastructure options become and the more likely that network upgrades have brought customers closer to owning what they need to support it.

Wilson says the dip in appliance purchases will be temporary. Financial services firms still need the technology to help comply with industry regulations that aren’t going away. So these customers will be back.

Tim Greene is senior editor at Network World.