Self praise and glorification is in no way intelligent, quite the opposite in my opinion.
I think it comes down to whether "smart" suggests "intelligent" or "smart-alec". Often it's the latter, and apart from being irritating in itself there's also the element that people who try too hard to prove their superiority just invite scrutiny to see if there's evidence to the contrary; the infamous spelling flame being a good example in that the culprit nearly always has some glaring mistake in their own diction.
In other words, it's probably not so much of a problem with someone who's quietly intelligent and sees no need to make a point of it, but it's likely to be a big problem with someone who feels the need to assert their awesomeness (whether or not it's actually the case).