Jim Lanzone CEO of Ask.com attributes the success of YouTube etc (and by extension methinks the failure of Ask.com etc) to the fact that users fail to link the big brands with new services. He continues,
"It's very difficult for a brand to mean more than one thing. When you get past two things you're really stretching it."
That seems to me to be a very push-marketing, product-centric view obsessed with delivering a message to your fawning acolytes. The reality of multifarious, individual customers is that they all have different worldviews and will infer different messages from your products/services and everything with which you surround them.
It is in fact inevitable that a brand will mean many things and it's your job to ensure that they're all outstanding things.