T-Mobile's Simple Family or Simple Business plans offer "Hotspot" from devices that offer that function (such as Apple i Phone) to up to 5 devices.
Since 2014-03-27, 1000 MB/month is free in the USA with cellular service.
This is done primarily because with a computer sharing the network connection, there may well be a substantial increase in the customer's mobile data use, for which the network may not have budgeted in their network design and pricing structures.
However, actions by the FCC and a small claims court in California may make it easier for consumers to tether.
On July 31, 2012, the FCC released an unofficial announcement of Commission action, decreeing Verizon Wireless must pay US$1.25 million to resolve the investigation regarding compliance of the C Block Spectrum (see US Wireless Spectrum Auction of 2008).
Some operators have asked Google or any mobile producer using Android to completely remove tethering support from the operating system on certain handsets.
Handsets purchased SIM-free, without a network provider subsidy, are often unhindered with regards to tethering.
While tethering may be allowed at no extra cost, some carriers impose a one-time charge to enable tethering and others forbid tethering or impose added data charges.