You control who gets to take your Poll. Maybe you want it to be open to everyone on Karma411. Maybe it's targeted for people living in Chicago or working for Microsoft. Maybe it's only for your Friends, a specific Group, or a List (Basic or Smart). It's your Poll. It's up to you.
Not unless they tell you. By default, all responses are anonymous. Neither the Poll creator nor individual respondents can see what Members took a Poll.
Need feedback from specific people? How about programmers in Poughkeepsie or Georgetown grads in Alaska? First create a Group and then invite the Group to take a Poll.