Basically, some people want there to be a mechanical similarity between peasants and beginning player characters. 3e arguably had this, since a first level Fighter was only a little bit different from a first level commoner. These differences, logically speaking, were kind of large- proficient with every weapon ever used by a major military, all armor, and whatever you got with a feat in 3e, but they were also mosty in the background. The up front stats, such as hp, attack bonus, and so on, were very similar to those of a peasant.
4e is a little different. A "1st level commoner" in 4e is probably a minion. That's an incredible fragile "chassis" in comparison to that possessed by even the weakest player character.
That being said, I don't think this is truly the only thing involved in creating a "just off the farm" feel. The way the PCs relate to other entities in the world besides commoners is important. A first level 4e pc is vulnerable to being killed by a (non minion) kobold. The typical trained human guard is several levels above the first level 4e pc. Because these are the most typical opponents faced by a low level pc, I think that this comparison is as important, if not more important, than the comparison to commoners the PCs probably never fight, and who's statistics probably never enter gameplay.
If I were genuinely interested in creating a "just off the farm" feel to a 4e game, I would start the PCs off as a part of a larger organization. Perhaps an army. I would use this to emphasize the PCs comparative weakness relative to the regular soldiers, whom I would stat up at around 4th level. Then the PCs rise from nobody recruits (with potential, see, eg, their power selection) to talented regulars, to elite soldiers, and then beyond (ie, to paragon tier), would be a major theme in my campaign, and a major source of the player's sense of satisfaction and accomplishment.
A related issue is the swinginess of low level 3e combat, in which a first level PC might have 8 hit points and be fighting an enemy who deals 1d8 damage on a hit. Sometimes people confuse this with a "just off the farm" feel. Its not. Its a separate issue.