I often build a limited size city (keeping the pop down to 3 or 4) and caravan/freight out food to larger cities nearby). I am aware of the cheat allowing you to continuously set up additional routes to the same city while only counting as one route, but I do not use it. Instead, if I need to send more than one food per turn to the same city, I set up a route to another city, and then have that city send its own caravan to the needy city in question.

It seems to have both positive and negative attributes. While extra food is always nice, esp. to high shield production cities (or a SSC), the AI seems to recognize the inherent weakness of these cities, and seems to attack them when possible (esp. on a coastline). In order to prevent the farming community from being captured militarily, I usually don't build city walls and station as many troops there as there is populace (1 for 1). That way, if the enemy defeats all of the troops, the city is destroyed rather than being a staging point for further enemy activity.