It all depends on your goals, protein powder is a supplement to a good diet, it simply makes it easier to consume more protein.

for me- its necessary, because i dont have enough protein to eat throughoutt he day.... its by FAR better to get your protein from real food sources, but its called a protein SUPPLIMENT. i usually have about 2 drinks a day with around 30-35g of protein in each drink. its around 160 cals for that, which is really good for the amount of protein your getting.