OK, the horticulturist, former nursery worker, current garden designer has to chime in here....
Gardeners are always giving "cuttings" to friends/ other gardeners, etc. to begin new plants. We own the plant; it is ours to do with as we please. Whereas a nursery/grower/garden center and yes, even Home Depot, pay for the items or put the time and effort to grow new plants from seeds, cuttings, tissue culture - regardless it all takes time and effort and someone is being paid to do it - so yes, it is stealing.
How is opening a bag of M&M's and taking a few any different? Well, simply put - it has a price tag on it and you are not paying for the portion that you are taking.
On a side note, something to consider is that different plants require cuttings taken from different part so of the plant, most need to include a node, rooting a woody portion of a plant is very different from a herbaceous one. Some require very high humidity, others will rot with too much and yes, there are some that will just root in a glass of water. What would you do after you get it home?
An alternative is to go to the GardenWeb forum, there is a board for plant exchange. See if you can trade something for the plants you want.
lele
Plant exchange