Clients often find it hard to swallow radical ideas if that's all they get to look at. It can be scary, even if they have the appetite for change. I'm finding this method - which i stumbled across in Ken Hudson's book The Idea Generator - useful for; generating ideas and selling them.
Ive adapted it slightly but it's the same thing.
Imagine 3 buckets:
Bucket 1 - Business as Usual.
Banner ads, microsites etc - the usual guff. Traditional methods easily understood.
Bucket 2 - Something a bit different, might be dipping toes into social web, engagement. Stuff like that.
Bucket 3 - Is the game changing, purple cow-ness. The out-there stuff that's going to get them noticed and talked about.
By aiming for bucket 3 when working up ideas at the very least your going to land a few in bucket 2.
And by presenting stuff in all 3 buckets clients can be more receptive to bucket 3 solutions when they can see why it's better/more innovative/remarkable than the business as usual.