As an ebay seller, I must say that I would love it if a knowledgeable buyer took an action that all but guaranteed me a greater profit.
However, screwing a legitimate buyer out of an opportunity to get a nice item at a very fair price is a genuinely rude and cruel thing to do.
Obviously, the bid was placed solely to short-circuit the Buy-It-Now opportunity. If the seller had actually wanted the item, he would have bought it. This is not a case where the end price is likely to be significantly below the Buy-It-Now price, and it may well be significantly higher.
Shame on you, *******!
The other reason to do Buy-It-Now at a fair price is to make a quick sale and get your money immediately. Tossing the process into auction mode ensures that the process will have to run its entire course and the seller will not see any money for a full week.
This is the reason that I will do auctions, or Buy-It-Nows, but never both at the same time.