Well going by my post hits it must be, my post here about Leaf Curl on Tomato's has had 12626 views and it is the top post on my blog.
Personally leaf curl on tomato's is the least of my worries, blight is my biggest. I would guess that the main problem when people tend to worry is when leaves look like this;
It can look a little scary for new growers of tomato's but if you read my post it is just a simple case of the plants protection themselves when they are trying to create less leaf area to cool themselves down. I never ever worry about this, but do try to make sure my plants are getting enough water at the correct rate when it is very hot. Remember the secret of watering tomato's is a little but often and you will not go far wrong. Tomato leaf curl or roll is not a disease, it is a physiological response of the plant to environmental stress.
Here are a couple of more photo's taken from Garden web forum
This plant looks pretty poorly, but I bet it was fine once the sun went down. I would say a little more watering would help. Tomato's do not have a large root system, so the soil should be fairly moist in really hot weather.
This plant is often how mine look when full of fruit, If you feel your plants are getting enough water, then try to shade your plants a little with some netting to cool them down slightly.
Of course there are other types of leaf curl which can be more worrying, like contaminated compost or even too much feed, you can see pictures of this on my post.
If in doubt please email me a photo, I will do my best to help with any problems relating to tomato growing, but sometimes it's a little like have a doctors appointment by email.