OF COURSE THEY WILL! My gosh, do you have any idea what goes on at a company struggling to keep its share price up? First, they will simply limit the employees that can get new smartphones. Then they will limit the ones who can even have them. Then they will go through large scale layoffs. Each step limits sales opportunities for all smartphone providers.
OF COURSE THEY WILL, if a recession hits and lasts. There is nothing essential about having a smartphone. If the choice is between food, rent and a smartphone, the phone is the first thing to go. Not only will they not buy new ones, they won't even pay for the data plans to support their old ones.
I hope you realize the PEG ratio is based on predicted growth. In that way, it is one of the most unreliable tools, because if the prediction for growth is wrong, the whole thing falls apart. There is nothing certain about predicting the future.
There is nothing new about the $600 prediction. Earlier this year, some were predicting it for the end of 2011.
I agree that you should know what you invest in, but it is unwise to ever think anything is certain. You should also look at how often the so-called experts are flat out wrong.