Can you profit on the stock market from Friend Request?
Life Invader and Bleeter are not competitors. They won't rise/fall with the other's misfortunes.
For a list of all competitors, and what missions you can profit from, go here.
Cyberclaw is correct.
If you want to make some easy cash. Buy 25000 ecola stocks (3-6 bucks) after the friend request mission and sell them when it hits 125 per share. (Later on in the story) Just keep any eye on the stock.