Maybe it only has memory for one month or something.

I am not arguing for it, though, so don't downvote me just because you don't like Homeopathy - I didn't invent or advocate it.

Edit: According to Wikipedia there seems to be a memory of a fraction of nanoseconds http://en.wikipedia.org/wiki/Water_memory (they seem to measure a specific kind of "memory", though). But what for example about waves, are they not also a kind of memory? Some waves last longer than a nanosecond.