I know that this would also depend on the integrity of the community, but I notice this happening a lot on Quora, and Yahoo answers. A lot of the time, the "best" answers aren't even structured arguments, just another "matter of fact" opinion.
This is a more difficult question than it first appears. Appealing to majority opinion is considered an illegitimate form of justification for a claim. Yet, in the StackExchange environment, we often take the highest-rated answer as definitive.
I'd say the major difference is that the high-rating is not intended to be taken as definitive --it is just there to help you find the best answers. Those answers, however, still need to be strong in themselves --that is, well argued and/or well supported with citations, references, justifications, etcetera. However, no claim is made that the answer becomes right or righter simply because of votes.
It may be a constant temptation to conflate rightness and popularity --but that is a constant temptation anywhere, that's why the fallacy exists in the first place. If anything, I'd say that consistent participation in SE could even reduce incidences of the fallacy, since it encourages the crafting of well-formed answers and also the critical examination and independent evaluation of other people's answers. (For whatever reason, SE seems to have accomplished these last two goals better than some of its rivals.)
The answer to your question is yes, if you are polling a general population.
When it comes to a community of interest, such as Stack Exchange seeks to build, the answer may be less clear. I believe the activities of the moderators and the rules that are enforced seek to avoid this fallacy. We are approaching - though probably not achieving - something like peer review.
However, even the most rigorous peer review can fall prey to the fallacy. Whenever I encounter an up voting criteria for crediting an idea, I think of what I call the Copernicus Factor. Had the survival of Copernican ideas depended on the approval of even his most learned peers, well, it is not that the truth about the structure of the solar system would have never come out, but it certainly would have been frustrated.
It is good to be reminded of your question regularly when communicating in this stimulating virtual environment.