I'm Canadian, and I say "folks". However, I usually tend to say it to sound different from others. I like the sound of the word, even though it's something mostly older people say. When I personally use it, I usually refer to my parents. It's often used in familiar company, or used to address people in a friendly, informal way. Hazel and Parker both have good answers. Folks is meant to be used in a familial setting to sound jolly and informal. It's meant to be inviting, so the speaker seems to be on a friendly term with you. It's also a little dated, so I often hear mostly older people use it. In my family I have heard: "You folks have better weather out here than we do." (folks = family members) "I told my folks about that." (folks = parents) From non-family members, I have heard: "Step aside, folks, the line forms on the left." (folks = people) "What can I get you folks?" (you folks = people)

I am from England in the UK. It is mainly used as polite but informal to a group of people you don't know, or a group including people you don't know well. I would not use "folks" when speaking to someone with considerably more status, unless to be intentionally disrespectful. "OK folks you can go through to the hall now." - Teacher or helper speaking to multiple parents waiting to see their child perform. OK folks if we could all just step back from the tape please..." security officer or other member of staff to members of the public. "OK folks we need to get going now, see you next time." said when trying to get my family to leave a party or club or event. "If any of you folks would like a drink there are bottles of water and cartons of orange juice on the table by the door." said by the person leading a workshop to the attendees.

Folks can informally mean "parents" or it can address a "group of people". I would never use it in a business meeting (or any other formal environment). I would also only use it to address a moderately sized group of people, or larger. I would not use it to address a small group of friends because the size of the group is not large enough. To be honest, I've only ever heard it in public announcements over PA systems, especially with pilots addressing the passengers on an aeroplane. I'm sure that North Americans could provide a more extensive list of examples. There is not a singular form of the word; "folk" is a genre of music.