Commingling Credit Card Purchases

[Matthew B.]

Is there anything wrong with making personal purchases with the business credit card, and business purchases with the personal credit card? 

Assuming at the end of the month the business expenses are paid from the business bank account and the personal expenses are paid from the personal bank account. 

What about using the same business credit card for multiple businesses?

I tend to use whatever card will give me the best rewards on the purchase, regardless of whether it's the business card or the personal card. It takes a little longer to sort out the statements at the end of the month, but it's a small price to pay for maximum airline miles/points.

I just don't want to get in trouble with the IRS, or expose my personal finances to business liabilities (i.e. corporate veil).