The current food truck phenomenon as we understand it is generally thought to have started in 2008 with Kogi BBQ truck in LA.  I should preface what is meant by the "food truck phenomenon" as actual food trucks have been around for over a century . The current food truck popularization has the following hallmarks:
- Fusion of cooking styles and genres. Taking 'gourmet' restaurant ingredients like duck and fusing them with your traditional tortilla to give you a duck taco for example.
- Social media: the likes of Twitter did play a role, if overblown at times, in driving these new age food trucks into the popular culture. 
Food trucks experienced a boom just as the economy started to tank. Restaurateurs who were hesitant to drop serious cash on launching a restaurant turned to mobile trucks as a less expensive way to sell food in a down economy. Social media has played a large role in not only making the trucks more accessible, but allowing them to cultivate the crucial element of community.
"It's the social aspect," says Kenny Lao, Rickshaw's co-founder. "It's really about shared experiences around food. I think what we're doing with Twitter is an electronic version of that share." He sees his restaurants as an older, established sibling living uptown, while his truck is like the younger brother fresh out of college and living in Williamsburg, Brooklyn -- different energies toward the same purpose.
- Combine the above two factors and you have hipsters paying 3X the price of a regular Mexican taco and feeling quite authentic and special about it.
Ok, that last bullet was my own commentary versus a factual observation. However, it is undeniable that what ever the demerits of the 'cool' factor may be, it has definitely thrust the gourmet taco truck concept into the mainstream and has opened people's eyes on the possibility of eating great tasting food out of a truck and experiencing food that they would normally not have in the regular restaurants that they frequent.
As for my own preferences, I will take a traditional lengua or buche taco for a $1.50 per taco out of my favorite Mexican taco truck any day of the week. I have yet to taste something better than that anywhere.
The first ever contraption I'd call a Food Truck was started by a man by the name of Charles ("Wagon Chuck") Goodknight. Of course then those things were called Chuckwagons and all the rage with cattle drivers. Chuckwagoneers would soon become more than just feeders of cowboys, the man on that wagon (we know only of one female chuckwagoneer, Betty "Six Fingers" Mills) was psychologist, logistics officer, purser, cook, and second in command.
Only a few years later, and this is where the Food Truck comes in, New York city saw a surge of so-called "Owls," food wagons that sold hot dishes to workers after the restaurants closed. That was 1890. By 1930, these wagons had almost completely been displaced by motorized versions, Chicago and New York were the front-runners here. With the 1950s came the flood of resold Army food trucks, which had been used in Theater Europe and Asia and become useless after the war. One of the first to operate such a thing was Giovani Ducci in New York who purchased it from the Army for $300 and began selling pasta and sandwiches to union laborers at the Port Authority in New York City.
Taco Trucks became popular in the 1970s in most any city. Unions in New York and Chicago started their own food businesses to feed labor (often under not-so-savory circumstances), and the first application for a mobile food business in LA came in 1973.
LA actually had a dying food truck landscape due to enhanced enforcement of non-registered food businesses in the 1980s, and only the dot.com boom brought a floundering industry back on its feet.
Oh, I should mention, the first motorized food business was run by Hank Spittle (with that name you don't want a food business) in San Antonio, Texas, in 1912. He re-purposed (it gets even less appetizing) a 1911 Garford Truck, which had been briefly used as a hearse by a local undertaker but abandoned due to its noise and propensity to break down on the way to the cemetery. In early 1913, the truck burned down, and Spittle went back to selling sandwiches from the back of his old horse drawn wagon.More questions on Food Trucks: