Have you ever bought anything from ebay/gumtree/craigslist?

I've noticed a few IPhone 4s for decent prices on Gumtree, but I've heard a lot of people have had bad experiences when purchasing second hand items (especially electronics), do you use any of these sites?

Nope.

Yes, usually posters from ebay

Never heard of Gumtree but have purchased quite a bit from Ebay and honestly never had a problem. I also recently sold a bunch of furniture on Craigslist and that went fine as well.

Well, I have bought from ebay but have never bought any electronics from there. The only things I've gotten are some Naruto merchandise (years and years ago, my dad had gotten it for me and apparently it all came on time and undamaged), and more recently some jewelry from China along with a pre-owned wallet. The jewelry was actually pretty good quality considering how cheap it was and that it was from China, and the wallet was pretty good, too. Everything came on time and was undamaged. So my experience with ebay is good, but I'm yet to purchase any electronics from there, so you may have a different experience.

No but my mom has for me and the stuff was fine

Use ebay they offer some protection

Lots of things.

I've bought concert tickets off someone and it was fine!