Just saying "we'll give ripples to everyone" is not very serious, for if XRP gets any monetary value, lots of people will fake identities in order to get as many ripples as possible. Instead of the CPU rule there will be a "cheating" rule.
That's probably true, despite our best efforts. But really, how much does it matter? It will just mean the giveaway won't be quite as effective as it could have been because it won't get as many users. But we know people are participating in the giveaways just to sell the XRP anyway. It won't make Ripple any less usable as a payment system.
Well, to be fair it might indeed not matter much. Lots of ripple proponents advocate for it in opposition to bitcoin, which they see as a speculative asset. They also seem to think that hoarding is bad, so a currency should lose its value with time. Therefore people might not be trying too hard to acquire ripples, so the amount of "cheating" might be low.
I has to be tried anyway.