If we have tags with just specific model numbers, we'll quickly have a sea of tags. People can mention the specific model in their question, and searching will turn it up.
We go with more generalized tags. We have tags for manufacturer (e.g., 'cisco', 'juniper', 'netgear'), and we have more general tags for ... and here's the discussion. (happening via upvoting of the answers below)
So tags like:
"cisco-2900" (or "cisco-isr" "cisco-isrg2") "netgear-gs724t"
My question, and so this discussion, it about TWO things: "manufac-..." in the tag (probably a communal YES) and then guidelines about what goes for the model "series" as that's a bit harder to decide.
(UPDATE) CLOSING THIS DISCUSSION--
Noone seems to object to having "MANUFACTURER-" prefixes on the tags. So I'm accepting answer here. I'm setting aside the undecided question of wether it should be "cisco-2900" (ambiguous) versus "cisco-catalyst" and "cisco-isrg2"