I work with bricks daily and I wouldn't mind of future bricks visitors associated my, presumably, totally awesome questions and answers with my company. Since SE doesn't have such a thing as a signature block, I think it might be worth while to establish, early in our coming-out process, our community's relevant tolerance for people pushing either their commercial or non-commercial sites.
It feels to me like this has probably been hashed out somewhere else, but what counts is what we want in our community. I know, for example, Joel S. recently talked about this on a recent SE podcast.
I personally feel that "casual links are ok, but don't be annoying about it" is a good-enough guideline.
There is a tension, in that we obviously don't want the site to be spammy, but also, we don't want to exclude the people that are literally professionals, either. The people that are expert enough to have their own site will always have a need or desire to associate their awesome answer back to their site. If they can't link back, then they are driving traffic away from their own site towards bricks.stackexchange.com. We don't people to have make that choice.
Here is a concrete example:
I recently asked this: LEGO Safety: Known risks and how to avoid them? I had already started writing a blog post on my website (Ascendly.com) on this topic and wanted to take advantage of bricks.se.com to make my post even better. It is my intention to link to the SE question in my post, and add link in my question back to my post. How would you react to such a link?
How did you feel that I inserted that link to my site in the above paragraph?
How would you react if somebody specifically mentions the they work with company X, or if they are a builder-for-hire?