Dear Spammer: I do have a donate button

The fact that spam making software doesn't actually tailor the spam to the page it's posted on or the site in general is obvious, but you'd think that someone somewhere in the spam scheme of things would insert a line of code that made it so the, "It's a pity you don't have a donate button! I'd certainly donate to this excellent blog!" (actual quote) spam didn't show up on a blog with a donate button.

Top of the page, right hand column.  With an image called, "btn_donate_LG.gif."  A simple check of the text of the page would reveal that it does, in fact, say donate.  It says it inside the name of an image, but if you're searching the page source that doesn't matter: run a search for donate and you get a hit.

It shouldn't be hard to make it so that the "I'd totally donate if you just had a button," (paraphrase) spam didn't show up on blogs with a donate button.  Just have a bit of code that makes it search the page's source for the word "donate" and if it gets a hit use some other flavor of spam on that particular page.  It's all still automated, it still requires no human oversight, but it makes it marginally more likely that someone won't be able to tell in one second or less that the message is definitely spam.