The logo is like the elevator pitch. – You can see everything you need to know about a company in an increment of time.
If the logo is good – you’ll remember that company for when you need their services. If the logo is really good – you’ll invest yourself in their services or product even when you don’t need it. If the logo is bad – you empty the memory of the company from your mind. If the logo is so bad that you never forget it – that’s great publicity that will never turn a new customer.