I don't think we need to ask about creating tags all the time.
It has been said several times: tags are one way to add categorization to questions, which should be used when they have value.
Part of the purpose of the private beta period is to define the scope of the site. This to some degree includes what tags we want to use.
So instead of asking "do we want a tag for X?", let's just create tags as we feel the need, assuming that they add some reasonable classification to the questions which they are attached to. Let's also do our best to avoid creating duplicate tags with the same meaning but different names.
Then in a month or two we can revisit the tags list and reconsider those tags which have only a small handful of questions. We can always fix wrong tagging later.