9 out of 10 people have no clue what bitcoin is but I would say those who are invested in it know what it is.
But Pump and dump is a real possibility... but there will still be those that use Bitcouns regardless of the dollar price. Them pumping up the price risks Bitcoin gaining in so much popularity that it becomes an independent Currency and the dollar obsolete.
They can manipulate markets but not Bitcoins. If people will value and use Bitcoins as currency then it wont matter if they pump and dump or how volatile the price is in dollars because people will not want dollars.