From this 2001 article:
Eric Horvitz... feels bad about [Microsoft Office's Clippy]... many people regard the paperclip as annoyingly over-enthusiastic, since it appears without warning and gets in the way.
To be fair, that is not Dr Horvitz's fault. Originally, he programmed the paperclip to use Bayesian decision-making techniques both to determine when to pop up, and to decide what advice to offer...
The paperclip's problem is that the algorithm... that determined when it should appear was deemed too cautious. To make the feature more prominent, a cruder non-Bayesian algorithm was substituted in the final product, so the paperclip would pop up more often.
Ever since, Dr Horvitz has wondered whether he should have fought harder to keep the original algorithm.
I, at least, found this amusing.
I think this is more of a reflection of computer literacy.
When my computer does something wrong, I assume its my fault. When my parent's computers do something wrong, they complain at it. Pretty uselessly.
I guess Clippy just makes people who don't normally over-anthropomorphize computers over-anthropomorphize enough to get annoyed.
Well, you often are not doing anything at all wrong when Clippy gets in your face. Its annoying because it reliably fails, until I disable it.