how can fruit not be good for you? the only unhealty smoothies i am aware of are ones which are based on ice cream or cream. it is apprantly better for you to blend the whole fruit to gain the full goodness, if you can put up with the little bits.
Yes they are good for you, but overdoing them can give you a loose bowl and give you a high sugar level, although its natural sugar. Just make sure you eat other food too, or if you are doing a smoothie fast, have some vegetable juices aswell to hold fire on some of the sugar.
You shouldn't drink too many if they contain Banana (for a number of reasons), but it's almost impossible to buy them without Banana in when buying premade ones in the shops.
Not that ones with Banana are bad for you but simply that oens without are much better.
they are and they contain lots of fibre too (unlike fruit juice)! try this is delish - banana, milk, vanilla ice cream, soft brown sugar and cinamon. Its not too healthy but absoloutely scrumptious!!!