Those of us in the army of hand-baggage only customers, will just see this as a price rise, and adjust our purchasing behaviour accordingly.
I can understand (if not approve) of this from FR's standpoint. When you have lots of people checking in online and not paying for airport check-in..... one begins to regard it as a subsidy of these passengers by those who checkin at airports and a lost opportunity to make a bit more cash out of the online checkin brigade.
I am unclear about one thing though. Will the online checkin fee be paid at the time of purchasing tickets, or will it not be payable until the time of checkin ? From a regulatory point of view, I can see it might be necessary to impose the charge at the time of ticket purchase. From a purely economic standpoint, it is presumably in the interests of FR to charge at the time of checkin rather than ticket purchase - this means that quite a few people who have already paid for a ticket are discouraged from flying, allowing FR to keep the full price for the ticket (the huge admin fee for a tax refund is pure business genius !) without having to pay any Govt tax / airport charges, making these customers exceptionally profitable.