Presumably they're worried about the dense jungle of HTML entities. The dense, well-documented, utterly predictable, routinely parsed jungle.
Of course they can parse them in some places, just not in others. And of course the big G. makes it really really hard to file bugs, so we just have to blog about it.
These characters are not allowed: &
To: Sergey From: Frosty Subject: Again with the Google problems! Sergey, You can make four billion dollars a year on text ads, you can map the known universe, you could probably put a man on the friggin' moon; but you can't write a regular expression. What gives? Is it the coke, or the bloated HR apparatus? Get Eric on this one, it's embarrassing!