What are the legal implications of using a customer company's logo in your marketing materials without its express consent?

I believe that, without their express consent, you would be exposed to fraud, false advertising, unfair competition, and trademark/service mark infringement. Think about it - let's say you used the well-known APPLE logo of the apple silhouette with the bite taken out of the side of it - you would automatically be associated with APPLE. So, your goods/services would automatically be attributed to APPLE, which they are not. APPLE would then have grounds to sue you for fraud, false advertising, unfair competition, trademark infringement, and the like.

I agree with Mr. Weinrieb and not to mention the bad position that could put you in with your customer who might no longer be your customer. If this is your customer, how difficult can it be to obtain their consent?