That "whole bunch of seedlings in a 4" pot" should be, as daninthedirt said, transplanted into open ground at least his suggested distance, though I prefer 18"-24". In good soil a basil plant will easily grow to 30" high and that much around. If you leave them in the pot that came in, you will get that number of skinny little, stunted plants and probably not harvest as much from all of them put together as you would from one plant properly planted. If you have no garden space & must use containers, divide the plants (if they are not already too large to do so) and put only 2-3 into a BIG pot--say 2 gallons, using soilless mix and organic fertilizer. Or one into a 12" pot. If your potted plants are, say, 8-10-12" tall, cut them back by 1/2, plant the bottom half (be sure you leave a couple sets of leaves on that half) and remove all but 2 sets of leaves from the top half. Put those cut stems in water and place the container in bright, indirect light. Within not too many days, you should see roots sprouting. Once the roots are 2-3" long, pot those plants up in more soilless mix. Stores sell cilantro/coriander in pots like this, too--way overcrowded. Cilantro should really be direct-sown either in open ground or very sparingly in a window box so it has room to really reach its potential. I sow cilantro every few weeks to have a continuous supply. It is a fast-growing, short-lived plant that bolts quickly when stressed or crowded.

Many people think that the flavor suffers as soon as the plants flower. Taste them and see how you like the flavor. If they taste soapy or bitter to you, you may want to pull them. If they taste strong but still OK, then harvest them. I've noticed that even when the raw leaves taste strong, they're still sometimes good enough for flavoring tomato dishes or for pesto, especially if mixed with a little parsley. So even if you don't like the taste when you nibble on the leaves, try them in recipes before you decide to give up on them.

Genovese basil grows to about a foot tall and has small leaves. More like little bushes. They too flower and the flowers should all be pinched off as if allowed to continue, the leaves yellow sooner and die. Basil can flower at any time, as its weather dependent as well as maturity of the plants that govern the fowering stages. Bolting is the term used for plants that shoot up flower stalks. In kost cases, there is no way for the bolted plant to revert back to something younger with no flowers present.

I found this older thread. Hope it helps. http://forums2.gardenweb.com/forums/load/cornucop/msg0415210727833.html?23 Personally, I would keep cutting the soon to be flowers and take some cuttings for propagation. http://www.gardeningknowhow.com/edible/herbs/basil/propagating-basil.htm I'm a new gardener so others here may be able to help you more.