Vera has repeatedly told me that “tagging” is a hard word to use in documentation because it has multiple purposes… whereas “labeling” is a bit more clear and more singular in its utility. Let’s face it, when you label something, it’s pretty clear what the before and after states are. When you tag it, not so much.
The other thing we have to consider is this: since Google is obviously throwing its hefty weight behind labels and not tags (consider Gmail, Picasa, your search history, the toolbar and elsewhere), we might do well to realize that the de facto “word” for this behavior will not be “tag”, but will instead over time become “label”.
Sure sure, we need consider what Redmond will standardize on, but from what I’ve seen of IE7, etc., they’re playing a game of catch up and will do whatever the consumer market standardizes on first. (Imagine that… what happened to that whole bit about needing a monopoly to innovate? Guess that didn’t work out after all, eh guys?)
Mind you I’m not advocating one or the other or suggesting that we all change course now (especially within Flock), but instead proposing that we think seriously about this now before the rift between the two starts to hit teh long tail and we have massive confusion between one term and another.