Wireless carriers' new flat-rate, unlimited data service plans will test the capacity of 3G networks and may spur unwanted traffic like text-message spamming, MediaPost is reporting.

In a new study, ABI Research warns that unlimited mobile Internet access will have the biggest impact on wireless networks as video and other applications eat up bandwidth, the article said. "The increased usage of SMS text-messaging alone can flood the network and impair the quality of voice calls, said ABI. Furthermore, the cost of increasing capacity to meet demand, especially in carriers' backhaul operations, can erode any gains from flat-rate plans."

All four major carriers are offering all-you-can-eat $99 voice plans, but only Sprint has gone as far as adding unlimited data to the package. T-Mobile, meanwhile, offers unlimited texting and picture-messaging; the other three plans still charge extra for those features.

Network traffic aside, lower-cost, unlimited data plans are the only path to wider acceptance of the mobile Web. Just as with CompuServe back in the 1980s on the desktop, few will accept paying by the minute, hour, or kilobyte. And while millions of customers have signed up for unlimited data plans today, most of them push the monthly bill well above $100.