Bing is from Microsoft, and Microsoft HATE Google (because they are taking their "control" of the web away from them).
I have not used Bing so have no idea how good it is, but it will take a while for people to get out of the habit of using Google.
I have to say Bing is a TERRIBLE name.
Mind you, I have to say that Microasoft are very good at grabbing "market share" for their products, like with Windows, Office, Internet Explorer etc) so it would not surprise me if they have some devious plan to try to get us all to use Bing.
I bet it is already the default search engine for Internet Explorer.