I have looked back through all the documents where I thought it was and I can't find it so either I made it up or I just haven't located the proper document first. Maybe I saw this statement:
they do increase your threat to the amount needed to pull aggro.
and inferred 130 since that is the maximum value required to pull off any tank. Not really sure.
Since I don't have any concrete evidence to support the claim I'll just concede to say,
since any good DPS will out threat you most any fight and especially on openings, taunts are your best friend for holding agro.