Here is omething on when and why the transponder turned off, with a hint that it may not have been deliberate. Guardian:
'The transponder – an identifying device that replies to radar signals from the ground – appears to have switched off two minutes after the last verbal communication with air traffic control. The Malaysia Airlines chief executive, Ahmad Jauhari Yahya, said a malfunction could not be ruled out. While an onboard plane-to-ground monitoring system known as Acars had stopped sending data back to base, the plane’s satellite transmitter had continued to communicate its presence to satellites until 8.11am.
“There [was] some functionality in the system, except the reporting system was disabled,” he said.'
So they aren't ruling out a malfunction but then again they aren't ruling out anything at this stage. So for me it is still no clearer. If the system has a malfunction would it still Continue to ping? Does it depends on the severity of the technical issue?