Obviously it depends on the concentration; I see Costco is selling (separately) Goji and Acai smoothies in their bottled juice section -- you could drink more than a shot of that a day. I think some of the appeal of this stuff is as an alternative vitamin (C) delivery system -- some diabetics have been avoiding orange and apple juices in recent years because of the natural (and worse, added) sugar, carbs (pulp), etc.
I know there are a ton of douchebags out promoting
an Acai drink packaged in a wine bottle as part of a network marketing business, but i'm in no way convinced it is worth it. I have seen this being sold to old people as a purported 'health supplement'.