After reading what everybody had to say about tipping "mousekeeping" on this board, I tipped them on our last visit. But my problem with this practice is that they are not considered to be "tipped employees" so nobody is looking for them to pay taxes on this income. It is simply not the nature of the housekeeping position.
Waiters/waitresses make less than minimum wage because of the expectation that gratuity will more than make up the difference, but the IRS insists that they report this money as income. If they don't, they are allocated tips based on either the gross sales per individual for the year (if they track it - most do) or per the restaurant for the year (to be divided amongst all tipped employees). Evidently, the IRS expects to see at least 8% of sales reported as additional income by the tipped employees. Been there, done that.
That said, you should not be expected to automatically tip housekeeping. If they want a job where their performance is consistently recognized/rated by a gratuity system, they can go wait tables. If their wages are too low, Disney should address that issue. I feel like they are simply doing their job. If, however, somebody goes above and beyond to meet special requests, then tip them.