My first thought would be drift from a weed killer containing glyphosate. (The most commonly used product of that kind is Roundup.)

I can be more certain if you post an image.

Yup. I have used both Roundup and 2,4-d based lawn herbacide recently. The latter was sprayed about 15 feet from the crop. After some research, I found pics that look exactly like the damage I have. 2,4-d is probably the culprit. Aparently 2,d-4 (ester) based herbacides can take on a gaseous form after application in hot weather which is probably what spread to the tomatoes. Thanks for pointing me in the right direction. Lesson learned, keep away from cheap spray-on lawn herbcides and certainly don't use them mid-season.

You wrote: "2,4-d is probably the culprit."

Not so. 2,4-D makes cells grow excessively. See this image from Cornell
http://vegetablemdonline.ppath.cornell.edu/diagnostickeys/TomWlt/2_4_D_Tom.htm

Your description matches glyphosate damage. See this image from Clemson University
http://www.clemson.edu/public/regulatory/plant_prob_clinic/fact_sheet_folder/herbicide_damage.html

You also wrote: "Lesson learned, keep away from cheap spray-on lawn herbcides ..."

Not necessarily so. Any herbicide can drift on the breeze or even just because of the turbulence from the spray. (A breeze is anything that makes the leaves rustle, even the slightest bit.)

Here is a link that might be useful: Clemson image glyphosate damage

...even the slightest whiff of RoundUp, near tomato plants will cause that.

I just noticed the same problem on my young tomato transplants. Thanks for the photo. In +30 years of organic gardening I'd never seen the symptoms, so was stumped on what the problem was. Some of the younger plants have already died.
A few weeks ago I sprayed the perimeter of the yard (on a still day, no less!) with Roundup to kill poison ivy.