That's not to say it couldn't have been hacked in a more traditional external-actor sort of way, but the timing is coincidental...
So that's the best estimate I can draw on the evidence here - My Space was probably hacked in the mid-2008 to early-2009 time frame.
From about mid-2008, everything started going downhill for My Space's business.
Facebook was on a massive climb and My Space was losing visitors.
But check the proportions in April 09: This data feels too late when we think back to the 1:5 and 1:3 ratios for Yahoo and Hotmail versus Gmail.