This has been discussed: It can not be done in a safe way, afaik. The problem is identifying such "illegitimate" blocks. There are legitimate 1-tx-blocks (eligius is mining them every day, as luke says). The grey data-series in my chart above reflects possibly legitimate 1-tx-blocks.
True, my memory isn't the best at times. It should however be possible to require that all blocks include more than one transaction as per one of the BIP proposals however then we are starting to move into the kind of regulation territory that I believe could quickly become detrimental to the project as a whole (and if this isn't workable with the current code feel free to spank me, I might even enjoy it
), so this needs handling with extreme care.
However I think that most peeps involved in this project as either miners, traders, users or whatever can more or less agree that the playing field has to be level for everyone and that sudden gaps in network service caused by incidents similar to what Eleuthria outlined a few posts back aren't acceptable unless they are caused by network luck, which this one clearly wasn't.
Stuff like this is also one of the huge barriers barring bitcoins wider adoption as people should be able to have fairly accurate ideas on when their BTC are where they're supposed to be. Atm I believe that the rule of thumb for transactions reaching 6 confirmations is 45-90min with rare spikes of up to about two hours, clearly that wouldn't have been the case last night which is imo fairly massive theoretical failcake for the project.
One of the corner stones in this whole project is it not relying on any kind of central authority apart from "the code". However in order for people to take this as a serious alternative to bank/payment-processor transactions there has to be an extremely consistent "level of service" for lack of a better term. Seeing as one of the worst possible situations with any kind of money/value is not knowing where it is or when it is supposed to arrive.