As all find out, there is no generic answer to this question. On two occasions I've eaten 0 calories for 30 days and dropped weight like crazy (disclaimer: I do NOT recommend this, and won't personally ever do it again). I've also done 1,000 cals a day for nine months and lost a couple hundred pounds. This time, I've done 1,500 and lost almost as fast (and much more comfortably).
So, I guess my advice is to eat at a comfortable level that still allows you to maintain a reasonably high calorie deficit. If you are significantly overweight, I don't think there's anything wrong with a 1,000 cal a day deficit assuming you are eating good food and making sure to meet your nutritional needs.
Of course, one should always take the advice of a doctor/nutritionist to be safe.
47 M 5'8"
May 4, 2010...... 440? lbs. (Start FitDay Size 60 Jeans)
June 19, 2010.... 393 lbs. (First Weigh-in)
June 19, 2011.... 229 lbs. (164 lbs. gone in one year :-)
Current Weight... 185 lbs. (Size 36 Jeans)
Next Goal 169 lbs. (07/04/12)
Ultimate Goal 165 lbs. (12/31/12)
The best exercises for weight loss are Fork Putdowns and Table Pushaways.