As mentioned it could very well attract robbing, a stronger hive could show up and fight and infiltrate the colony. Once the stronger colony gets a taste they show up en masse, potentially putting quite a hurting on your colony, possibly wiping them out.
Community feeding works as long as all the hives are being feed, not just one or two. Community feeding is best accomplished by mimicing a natural source such as in the middle of blooming flowers or near fruit or flowering shrubs. Try to make it so all the hives have to travel the same distance and that all have access.
Place capped honey frames inside the hive and reduce entrance. You could set up a community type feeder a good bit away from your hives, so all of the foragers meet at a neutral location.
If feeding from capped or extracted frames it is best to place the frames in the hive even if only a super above the brood area, but be sure to feed evenly to all your hives. Feeding one hive and not feeding the others is the best way to set off a feeding and robbing frenzy that I know of.