See, I don't buy that inter division (or conference) thing in the NBA depending on your direction...maybe in the NFL where you play twice per year and it's 12.5% of your schedule, but in the NBA, divisional games (4) accounts for slightly less than 5% of your schedule, some conference opponents you only play twice per year so you are down to 2.5 percent of your schedule.
I think a lot of other factors come in too (consider the knicks and zach randolph for instance) depending on the player, but i don't believe in the blanket 'don't trade' things, because you are limiting your options, if you say no conference, you cut out slightly less than half your trading partners...and with a brett favre, who is only playing for one year, if it's a crap team in your conference, who cares if you trade him to them if they get the best deal you might not even play them this year