Ellipses at the end of unfinished lists

After reading a question wrongly posted on programmers.SE and especially the post at PR Daily quoted in one of the answers, I have some doubts about the usage of ellipses.

In French, ellipses are also used when there are several elements in a list, but only a few are enumerated. Example:

Stack Exchange websites include Stack Overflow, Server Fault, Super User...

I always thought that in English, the usage of ellipsis in this context is not very correct, would never be used in books or press, and must be replaced by "etc.", but is still used in email communication. At the same time, the quoted post from PR Daily doesn't mention this usage.

So:

• Are ellipses used in emails by English-spoken people at the end of unfinished enumerations?
• If yes, what are the guidelines for this usage of ellipses? Is it totally wrong to use them for unfinished enumerations?

It is completely normal and understandable to use an ellipsis (or just three dots if you care to make the typographical distinction) for unfinished, continuing, lists. It's often used particularly to strike a humorous note. "There's my ex-wife Cindy. And there are my ex-wives Helena, Georgia, Audrey..."

You are right that it is probably "rather informal": you'd probably not use it in, say, a novel. I'd say you'd see it in magazines fairly often. More "stuffy" newspapers would avoid it, it would not be in their style guide.

It is 100.0% understandable as an "unfinished list" to any anglophone.

Note that you would not have a comma after the last item before the dots.