Again in 2010, two tomato care questions have reappeared here: "Should I prune off (snip off, pinch out) the first tomato flowers that appear, in order to get more tomatoes later?" And, "Do I need to prune my tomato plants?"
Those early tomato flowers, especially if the weather doesn’t cooperate, will fall all by themselves, thank you. Your assistance is not needed. And if you want to prune your tomato plant, you better have a damn good reason.
Flower drop and tomato fruit set failure can happen in May and June for a number of reasons, including night temperatures below 55; daytime temperatures above 90; excess nitrogen fertilizer, too much shade, too much smog, plants set out too early in spring, or planting the wrong variety for your area (Beefsteaks and San Francisco is not a match made in heaven).
However, by removing those flowers once they are in a situation where they can be pollinated successfully, what is accomplished by removing those flowers? FEWER TOMATOES! And, unless you are trying to stop production, it would be counterproductive to your ultimate goal: shoving that beautiful red orb into the face of your non-gardening neighbor in July, singing, “Nyah, nyah, nyah!”