Website Beyond 3D is reporting that up to a third of PlayStation Portable’s processing power is reduced while utilizing the handheld’s Wi-Fi capabilities.
Using the Firmware 3.5 clock control function, tests recorded the system running at its peak performance of 333mhz; enabling the Wi-Fi adapter, however caused the frequency to drop down to 222mhz during gameplay. As a result, it is speculated that developers may opt to degrade the performance of the one player mode in titles that feature network play, though those that are completely offline will remain unhindered.
When contacted, Sony declined to comment any speculation. Expect more details as they become available.