Leonid predicted that, as the site became better known, we would get more newbie questions. Questions like this one. I don't think we have yet seen an avalanche of such questions, but inevitably we'll get a few each day.
In responding to these questions, I hope we never lose sight of what made us start this site and made us work as hard as we have to make it a success: our enthusiasm about the product. Most of the regulars and high-rep users are not WRI employees. We are plain users who enjoy the product and just want to show off what it can do. At some level, our activity here is a kind of advocacy for the product.
Mathematica is a niche product. Very often, users are on their own with no peers in their workplace with any expertise. Of course they make simple mistakes if they have nobody to ask and the documentation is complicated. Mathematica.SE is the first general help site for the product that didn't have huge email-moderation lags. It is no wonder we have become one of the higher-traffic beta sites in the StackExchange network - something like this site was sorely needed!
Don't get me wrong: downvoting and closing the question I linked to above was exactly the right response. But as we do so, I hope that we remember to do so in a way that doesn't demoralise the first-time posters with simple syntax and other errors, but makes them feel welcome nonetheless, and keeps them coming back with better questions.
I guess this post is just a reminder of what made this community such a community - including the relatively low rate of downvoting and the welcome comments to new users. I am not suggesting that we should refrain from downvoting posts that deserve it. I am suggesting we should continue to post those little welcome comments and generally try to convert first-time users into constructive users with a stake in the site. This will, I hope, inoculate us against some help vampire behaviours and keep Mma.SE the funnest site for technical computing Q&A.