Three Tips for Saving Money on Mobile Plans As mobile data plans move to a pay-per-use model, you and your business will have to learn to work around them.

All-you-can-eat never lasts forever. That's the story in mobile these days, as mobile data plans--the kinds that let you surf the web and download apps on your smartphones and tablets--move to a pay-per-use model. Businesses, consider yourselves warned: Going over the limit can result in hundreds of dollars in overage fees.

When the mobile internet was slow and ugly, unlimited data plans made sense. But as mobile apps and streaming video came into vogue, suddenly those mobile data networks started getting bogged down. So out came the tiers and the caps and the throttling. Here's what it all means.

Reality: Almost no mobile operator offers truly unlimited data plans these days. AT&T famously moved its iPhone data plans to tiers first: 200 MB of data (enough for light surfing and e-mail) for $15 per month; 2 GB of data (fit for streaming music and video) for $25 per month. Verizon is planning data caps soon, while T-Mobile continues to offer unlimited data--unless you use too much, in which case they'll throttle back your speeds for the rest of the month. And no, most carriers won't let users share pools of megabytes of data as they do voice minutes. Every smartphone user needs to be vigilant.