prettyfacetay, Sherry is correct. BUT if you know the username of the person you are searching for, you can go to www.google.com and type in the username. It will bring up the persons ask.com profile and you can get to their profile that way :)
Not search for somebody, no. But, you can find people you want to read what they are asking /answering by "following" them. You can do this by checking the "follow" icon, when you come across something they have asked or responded to.