Although this could theoretically happen every day, and could happen for busts over even small ammts to make a news story about 'internent drug dealing' one thing to keep in mind is that police like to get big busts, or at least reasonable size busts.
Police don't take the trouble to plant an UC wiht a group of kids who pitch in once a week to buy a 1/4 oz of weed to split up. Police also will not waste too much time when it looks like they are not going to get up a chain to some significant amt of product. I can guarentee you the bust in florida, if it happened, was not over an 8ball.