No matter how delicious those young greens may be, you need to know when the crop has been sufficiently thinned. Think about the mature size of the plant or root. If you want a 2-inch beet, leave that much space between seedlings. If you want a lettuce with a wing span of 12 inches, give it 6 inches on each side. But a few will wind around each other at that spacing, which is amusing and still tasty.
All bets are off with rutabagas.
Given enough spread space and fertility, they will get really, really big. Joy to the rutabaga lover. Not all crops should be thinned by yanking excess plants out of the ground, even with a rake. Pulling up one plant is likely to damage the neighbor on both sides, because their roots will be intertwined. If it appears that the peas and beans will be overcrowded, thin them immediately after they germinate, before the roots have spread too far.