Useless Ethereum Token – The world's first 100% honest Ethereum ICO
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Also, it's possible to get a side benefit from this, because instead of a big buying transaction you can split it in many small transaction and get additional worthless useless tokens. I'm not sure if this consumes more gas that is discounted. If you split the transaction in N parts the amount of additional gas is O(N) but the additional tokens is O(N^2) (at least initially), so at some point you must get more tokens. (I'd like to read a complete analysis about this, with the actual constants.)
Anyway, just in case: This is not financial advice.
You're absolutely right, this strategy does encourage contributors to wait until the end of the crowdsale period, since they'll get more tokens for the same cost. And you're also right about multiple transactions being more fruitful, since the amount of additional tokens isn't dependent upon the contribution amount; a previous version of the contract would have permitted 0 Ether transactions to effectively get free tokens, but I've since changed it to require a contribution of at least 0.01 Ether (three bucks, give or take a few cents) in order to get any tokens above and beyond the contribution amount. In theory, this will encourage many smaller (but not tiny) transactions spread out across the crowdsale.
But at the end of the day, does it really matter? The tokens are useless and you shouldn't buy them. Seriously.