No one can dictate what all the exchanges and wallet software providers will do, so a variety of approaches will be tried.

This brings risk when a user accustomed to a particular decimal point location switches to another client.  A user in the habit of typing "100" for 0.1 BTC may accidentally overspend by a factor of 1000.

So we should advocate software that provides customizable transaction/fee size limits and warnings, regardless of whether there is a choice of btc/mBTC/uBTC preference.

We need warnings such as:  "You are asking to send 270 BITCOINS but you have requested alerts for payments over 2 BTC.  Previous payments to this payee have not exceeded .5 BTC (500 mBTC)."

And:  "You have not included any decimal point in the amount of this transaction.  Do you really intend to send 527 BITCOINS?"

And enforced limits such as:  "You have specified a 0.5 BITCOIN FEE for this transaction.  Your maximum fee setting of 0.5 millibits currently prohibits this."


(To limit such risks, one should of course keep higher balances separate in cold wallets.)