OK every single MR rep will tell you no problem you can have both a BIZ and PER card and have all the MR points all dump into the same "bucket" at MR.
Here is why you should NEVER EVER EVER do this.
So many promotions like the 10k "INSITE" search tool from AMEX have a code. You can only get credit for a code one time. You can under this promo, if you have 2 cards, get points for each card, but only if you have two MR accounts.
http://www.flyertalk.com/forum/ameri...ng-insite.html
I would guess there are many other like this as well and will get many more points by having they as two cards and two account!
Forwarded is forearmed everyone!