Generally speaking, I would agree that validation is often too strict.
Google seems to handle this well, however. In fact, I seem to recall Matt C. once saying that the VAST majority of websites don't validate. I think he may have been talking strictly about HTML, though.
Validation isn't a ranking factor, of course, and most prevalent browsers will compensate for minor errors and render a page, regardless. So I really wouldn't be too concerned about validation just for validation's sake. As long as your pages render in most common browsers and neither page functionality nor user experience is adversely affected, I'd consider it a non-issue. As to whether a bot could be fooled into thinking the head had ended and the body had begun, I suppose it's possible, but I've never seen it happen, even with some absolutely horrible coding.