my wife very nearly got trapped by this. Her "un-chipped" passport was near its expiry and I went onto the web to see if there was a requirement of "at least 6 month's validity" or the like from the US and discovered that there was not but that her unchipped passport would not work for our trip to FSO in June.

Yes it is the travellers responsibility to check, but IMHO, some blame should also be placed on the US for introducing this rule and for not exactly publicising it (I could not find any reference to it on the US DHS website); some credit should go to the UK FCO for spelling it out on their website and BA can get both credit for mentioning it and a black mark for leaving it so close to the date of travel.

Anyway, a passport renewal can usually be done very quickly and an ESTA usually takes a few seconds to get so don't panic yet.