[Doc]

Pocket tens against 9 random hands is 17% to win at a showdown. Against 4 random hands it is up to 36%. If you don't raise then you are letting 9 players make an easier decision than if you folded. If you do raise, at least some of them will fold. I don't want to play 10's against 4 players though - I want it heads up. Thats just the way I play tens. Nines I'll play like you guys advocate for 10s

Aces I'd NEVER slowplay from under the gun UNLESS I was pretty sure it would be raised by someone. Kings likewise. I'm guessing most players are the same. I think most people would agree on the following idea:

Get your big pocket pairs against a small number of players
Get your small pocket pairs against many players and hope to make a set

Where we might differ is what constitutes big and small - Tens are my dividing line. Other people might use Jacks or even Queens. Depends on the players you are up against I guess. Most times when I play, a large number of players will fold to 4XBB raise unless they have something. That something might be another pocket pair or maybe something like AQ, AJ, KQs - maybe JJ. With AK, AA, KK, QQ they'll usually re-raise. If I call and hit a ten in that scenario (the raise) I'm taking all their chips. If I don't and an overcard hits then I'm done.
If I just get called then it is down to the number of players I face. I'd imagine most of you would open for a raise from middle position with tens? If so and you get several callers, how do you decide to proceed on the flop? Same way I do here......

Tens are my dividing line because they are such a key card - involved in more straights than any other card etc. If I hold two and raise pre-flop, then it makes it less likely that someone else beats me with a straight. You've got equity in the pot against random hands. You can stand a raise. You have the 4th best hand pre-flop. That says raise to me.