Which card issuers do not forbid churning for these credit card with miles signup bonus? By churning, I mean signing up for the offer, meet spending requirements and cancelling once I get the miles.

Churning typically refers to the ability to sign up for a card, receive the sign up bonus, cancel the card, and repeat the process with the same card, over and and over again. If you're still interested in signing up, getting the bonus and canceling the card, you can do that with almost every card. There are very few cards that have a required minimum amount of time that the account must be kept open.

Since this is a generic cr. card question I'm moving it to the CCP Forum.

Have you tried a "search" in the MB and CCP forums? Use the word "churn" or "churning". There is a lot of info already posted on this topic.

chase and citi limit this. chase will even take the points back (in theory, hasn't happened to me...yet)

amex is getting this way too, as far as targeted offers go.

Those are the big dogs of the CC signup offer world, so you're left with the pittance that is BofA and local banks.

I don't understand your post. FIrst you explain churning (correclty), as "repeat the process with the same card". Then you say "you can do that with almost every card" but only about applying once and then cancelling. That's not churning according to the definition you just gave!

AMEX tends to not allow churning "ever" with the exception that if the new bonus is bigger than the bonus you got years ago, they may give you difference if you apply for the same card a second time ever.

Citi allows you to churn AA cards (and presumably some others) if you wait 12 to 18 months between applications "bursts". (Citi lets you apply for two AA cards at the exact same time -- though not close, it has to be just about the exact same time to work! -- and that's what I mean by "bursts".) Btw, that's the Citi personal cards calendar, the business cards calendar is completely separate and different.

I'm less clear on Chase, Barclays, and BofA current churn policies (with regards to repeating the same card).

I opened first Citi HHonors in March 2011. Met spending requirement in 1 month. Cancelled shortly thereafter. On Sunday, I accidentally (due to error messages) registered for 2 Citi HHonors cards (50k bonus each). Honestly, I just wanted to try to open one, due to rumors of churnability. I'm on my way to annual spend requirements.

There also are rumors of Barclays US Airways Mastercard being churnable. I have a 2nd app in for this card, after 4-5 month wait, and am waiting to see what happens.