this freaking injecting poultry and meat with water thing really pisses me off.
While it is used excessively these days, for the most part, injecting a low concentration salt solution into most meats goes a long way in helping to develop flavours; preserve the meat; and keep it moist during cooking.
We often replicate this method when we brine foods (which most people don't do enough of these days). While brining is far better as it involves various other beneficial outcomes, a small injection of brine is a good thing for most cooks.
At the end of the day though, it is more commonly used by mass manufacturers to bulk up their products and they have lost the plot in this respect. Many of the chemicals/additives added to processed food serve no purpose apart from helping certain cells in meat retain more water and some of these chemicals are dubious to say the least. A prime example here is ham, where they chemically manage the pH level of the meat as a higher pH content results in better water retention. You then have the various phosphates and emulsifiers added to create artificial cells which retain even more water. They then add sodium nitrite as a preservative and sodium erythorbate as a curing accelerator. It is then compressed under incredible amounts of pressure to fuse the chemicals into meat and to form the square and round shapes we know.
Store-bought ham is some of the most processed meat in the industry and it bears on resemblance to what real ham should be. It is pretty much the same process they use to create polony, only they use more chemicals in ham...