What incentive is there for a miner to not cancel his own 'real' txs It is said that a Bitcoin miner attacker with enough CPU power to outrun the entire network is better off mining honest bitcoins - which is not correct since by creating a false block chain the attacker already wins the coinbase on the way, just like he would if he behave honestly.

Actually, an honest miner has all the incentive to defraud by adding to his block transactions that cancel his own 'real' transactions. 

Or am I missing something?

EDIT- and maybe an answer

Let me give an example, lets say Alice owns a very big pool (big pools had known to create up to 6 blocks in a row), also Alice buys something from Bob for 1 bitcoins every 10 minutes.

Alice could try to do double spending of each of her payments (by passing the same bitcoins to herself) and use the second transactions in the block she is mining.

Note that this is all completely legit.

If the pool solves the proof-of-work, then her 'real' txs will be canceled - Bob can wait 10 minutes to see if the transaction gets confirmed or not, but it might not be enough in the case that there was a fork.

Conclusion:

A owner of a big pool can try to create doublespends but he will win his btc back only in rare occasions when:


there was a fork 
Bob didn't check the fork, and didn't wait enough time (e.g. 1 hour) to see if the transaction was confirmed
The good that Alice bought is not associated with any physical address (so that Bob cannot find Alice and claim for his money).
It is a short term gain only, as bitcoin would very quickly lose its value as people realize that holding one's wealth in bitcoin has become a bad idea. Behaving honestly gets you income until such a time your hashing power decreases.