3G phones have the capability of doing great things at data speeds approaching those of home Internet connections. At least, that's how cell-phone companies want you to think. Using that same thought process though, any and every child born in this country has a chance of someday becoming president. In both cases, these goals are possible, but not necessarily probable. Now that all four of the major U.S. cell-phone companies have, or are in the process of rolling out high-speed cellular data networks (EV-DO in the case of Verizon ( VZ) and Sprint ( S) or UMTS/HSDPA from AT&T ( T) and T-Mobile), it's time to take a look at just how fast these networks allow data to flow. EV-DO (Evolution-Data Optimized) works on CDMA and TDMA networks. In its latest form, called Rev. A, it is capable of data speeds approaching 3.1 Mbit/s. UMTS (Universal Mobile Telecommunication System) and HSDPA (High Speed Download Packet Access) are the preferred high-speed systems for GSM-based networks. On paper, UMTS/HSDPA systems can support down-link speeds up to 14.4 Mbit/s. In the future, HSPA+ systems might provide as much as 42 Mbit/s downlinks. All of these numbers from each of these systems are the extreme upper limits. What that really translates to is if you're outdoors, in a very secluded area, with no one around for miles -- and your phone has perfect "line-of-sight" connectivity to the transmit/receive cell and you a fully charged battery -- then, maybe (if the weather is just right and the wind is blowing in a favorable direction) you could, possibly, begin to approach these upper speed limits.