If uses typing the all caps verison of AJAX by accident really is a problem then we should keep the disambig at the top of the page, though I dislike it as it's messy and and we'd only be doing it to help users who have made what amounts to a typo. It's certainly preferable to redirecting AJAX to the disambig (see the relevant alk page for the reasoning on that). 

 But, again, I have real trouble beleiving that this is really all that much of a problem or that it happens very often.