AT&T, Verizon and T-Mobile have asked Google to prevent their users from being able to access tethering apps. Those carriers want subscribers to have to pay their rates for using their smartphones for wireless or wired internet access. The apps will still be available online, but they are blocked from users of those carriers on the Android Market. The workaround is to go to the developer's site, but you'll have to do a web search for that. You won't find searchable descriptions or ratings on the market.
AT&T has been sending out warning emails to their smartphone subscribers to ensure that they pay for use of their phones for internet access for other devices, like laptops.T-Mobile charges an additional $15 per month in the U.S. for using up to 5GB of data. Verizon wants an extra $20 on top of it's already pricey $30 per month for data up to 2GB.
If you're already watching your retirement money, it may be worth the extra effort to learn to download these apps outside of the Market.
For more information, see the article on cnet HERE.