I believe Chase starts forcing the 6 month active account sometime this year. The requirement is specified on the form, either in print or on the web, saying the miles will be taken back. I recalled reading one post in the last couple weeks mentioning being threaten by the supervisor when calling in to cancel within 6-month.

Even though I haven't spot any post reporting bonus miles being withdrawn upon early account cancelllation, I do know First USA (Now Chase) was good at deducting miles from creditcard activities. There were two instances in the past that I had two refund credits in the month that I didn't generate any other activity. Those two month, my United MP account statements were showing (-4) and (-13), respectively.