WDTV Live Supported Adapters

List of Officially Supported Adapters
"The following devices have been tested and are known to be compatible with the WD TV Live HD Media Player
 * (using firmware 1.04.31_V) and the WD TV Live Plus HD Media Player (using firmware 1.04.31_B)." (WDC)

Bugs
There was a bug in firmware version 1.04.17_B for the WD TV Live Plus which caused some wireless adapters that had worked previously to no longer work.
 * The 1.04.18_B update claims to have fixed this bug with the following release notes:

* Resolved USB FW update issue found in 1.04.17_B. * Resolved issue with Airlink Golden 150 and D-link DWA 131 Wifi adaptors not working with 1.04.17_B.

Possibly compatible devices using the following chipsets...
Keep in mind that the WDTV Live will only function (out of the box, anyway) with chipsets which have available drivers on the device. The USB ID for the device must also be within the driver, so devices with vendor specific USB IDs (of devices not in the official list) may not work. The default USB IDs, however, should generally be within their respective drivers. Even with both of those requirements fulfilled, it is still possible that certain devices will not work. Do your due diligence....

Default USB IDs

 * RT2770: 148f:2770
 * RT2870: 148f:2870
 * RT3070: 148f:3070
 * RT3072: 148f:3072
 * RT3572: 148f:3572

Default USB IDs

 * RTL8188SU: 0dba:8171
 * RTL8191SU: 0dba:8172
 * RTL8192SU: 0dba:8174

Default USB IDs

 * AR9170: 0cf3:9170