There's been some speculation on what a +4 spoon would do, so I figured I'd weigh in as an expert of sorts on D&D.
Really, it depends upon what it's being enchanted for. I think the default assumption is that it's enchanted as a melee weapon, and so functions as a diminutive one-handed weapon that does 1d2+4 damage - given the strength of such creatures, you're probably looking at 1d2 damage after the strength penalty, which is a modest improvement over the 1d2-4 (minimum 1) an unenchanted spoon would get you, for the reasonable price of 32,300 gold pieces.
For justification of this, that effectively makes it a diminutive club (d6 stepped down 3 times); it would be capable of being wielded as a light bludgeoning weapon by a tiny creature (something about cat-sized) at a -2 penalty, and not effectively usable as a weapon by anyone small (halfling-sized) or bigger.
An alternate explanation would make it a spoon which gives you a +4 bonus of some sort to a spoon-related skill, which would then be about 4000 gp (twice normal for not taking up an equipment slot).
There's been some speculation on what a +4 spoon would do
It gives a +4 bonus to the dexterity check to avoid dropping ice cream on your clothes, or others' clothes. However, due to a quantization issue in the laws of physics, exactly one-twentieth of all scoops still result in critical failures, and many of those failures lead to food fights, which is where the +4 to hit and damage comes in.
Update: Please post new comments in the latest HPMOR discussion thread, now in the discussion section, since this thread and its first few successors have grown unwieldy (direct links: two, three, four, five, six, seven).
As many of you already know, Eliezer Yudkowsky is writing a Harry Potter fanfic, Harry Potter and the Methods of Rationality, starring a rationalist Harry Potter with ambitions to transform the world by bringing the rationalist/scientific method to magic. But of course a more powerful Potter requires a more challenging wizarding world, and ... well, you can see for yourself how that plays out.
This thread is for discussion of anything related to the story, including insights, confusions, questions, speculation, jokes, discussion of rationality issues raised in the story, attempts at fanfic spinoffs, comments about related fanfictions, and meta-discussion about the fact that Eliezer Yudkowsky is writing Harry Potter fan-fiction (presumably as a means of raising the sanity waterline).
I'm making this a top-level post to create a centralized location for that discussion, since I'm guessing people have things to say (I know I do) and there isn't a great place to put them. fanfiction.net has a different set of users (plus no threading or karma), the main discussion here has been in an old open thread which has petered out and is already near the unwieldy size that would call for a top-level post, and we've had discussions come up in a few other places. So let's have that discussion here.
Comments here will obviously be full of spoilers, and I don't think it makes sense to rot13 the whole thread, so consider this a spoiler warning: this thread contains unrot13'd spoilers for Harry Potter and the Methods of Rationality up to the current chapter and for the original Harry Potter series. Please continue to use rot13 for spoilers to other works of fiction, or if you have insider knowledge of future chapters of Harry Potter and the Methods of Rationality.
A suggestion: mention at the top of your comment which chapter you're commenting on, or what chapter you're up to, so that people can understand the context of your comment even after more chapters have been posted. This can also help people avoid reading spoilers for a new chapter before they realize that there is a new chapter.