It can be hard and it can be easy. It has so many variables to be considered.
Now, sure it easy to go down to the end of your street and throw some seeds on the ground and watch a couple of them sprout. Its a whole different thing to have those seeds at the end of your street turn into ounces of good ripe bud a few months later.
If someone can grow outside in their backyard and have alot of constant control over a couple plants, its going to be alot easier for them then for the guy who drives an hour away, hikes 30 minutes into thick brush, hills and forest and is trying to grow dozens or even more plants that they can't protect and tend to every day.
Sure it's easy to throw a few seeds on the ground. It isn't too hard to grow one in your garden much like it would be to grow a tomato plant but that's about as far as the "easy" part of it goes.
Take a look at browndirtwarriors videos of his outdoor guerilla growing. Even though all you see is a tiny fraction of the effort and time he has to put in on those plots, you'll get the idea that it is very far from being easy to be a successful guerilla farmer. Most people don't have the knack, fortitude or the balls to make it through one season. A successful guerilla grower is a hardy breed of human, that's for sure.