This would only apply to "help me out" forums, not Foo:

I think that the original poster should have their email notification flag turned on by default. They would keep getting a special line of text encouraging them to update the thread with their results.

Optional BOFH feature: The OP cannot turn off email notification until some minimum period has elapsed or until they come back and add a [SOLVED] flag to the title. This would "encourage" them to return, whereas they were not planning to do so, so no loss if they don't.

I often turn off that option to get notification of replies at other places because i've been sent too much email by them. I guess the no option solution would change that. Would it stop me from posting, knowing that in advance? I don't know, but it would make be double check before submitting a question.

I would have thought that e-mail has to be the best option to win returns from those that have forgotten.

Often those one-time posters are searching for a solution of their problem. If they have found the solution on another website or they have found another forum where they received a fast and decent response, they won't return to a slower forum.

One of the success parameters I have found is to give a first quick response. It doesn't necessarily have to be the answer, but a sign that they have been recognized and are welcome can do wonders.

+1 to what lammert said. The quick response could be a site or search keyword suggestion. Many times they will then offer what they have already tried if it wasn't in the original post.

No one wants to talk to themselves in a dark closet ;-)

Could be spammers too. Some forums don't set a time limit for editing or they might submit with a plain signature etc.

They come back in a few days/weeks/months when the thread is buried and edit the post or signature.

Do you have any strategies for re-engaging these one-post wonders? Is it worth the effort?

Yes. I ignore them. After 60 days of no activity I delete membership (not their message). As others have said these are drive by gimme-an-answer-quick visitors not worth the time. And because of that OBVIOUS engagement I won't expend any effort to beg them to return.

Pick and choose... do that when time and effort makes sense. After 20 years on the web I've come to the conclusion it is not worth the effort.

Pick and choose... do that when time and effort makes sense.

Once you have an automated system to remind them that they registered and are a part of the great community, time and effort are negligible. I send as many as 8 emails over time to remind my one-post-wonders what they are missing.

I just prefer to not add to the unsolicited emails in inboxes. Different strokes for different folks.

Dataguy, you may well be the owner of one of the sites where I was a one-post-wonder. Received about 8 emails over a period of more than a year to reconsider coming back. These emails just strengthened my feeling that that forum was the wrong place to spend my time on. If you have to beg for participation on your forum, something is fundamentally wrong. Members have to stay voluntarily.

Maybe there's a happy middle ground. Some people actually DO lose the link to where they've posted, and might appreciate a followup message a day or two after they post without returning to the site.

Perhaps after some period of time one more message might not be too intrusive. I'd consider combining tangor's and dataguy's strategies and, after a few months, ping the user with a message like,

Thanks for participating in our Widget community. We hope you found it welcoming and helpful. Since you have not returned, we are planning on deactivating your account.

While you are certainly free to return in the future and re-register, if you want to avoid that process as well as keep your current username, please click the link below to return to our site.

I haven't actually tried this, but I would think that few recipients would consider it spammy and that some percentage of recipients would return to the community via the link.

Just to clarify, on my site, if you never come back, you would only get a maximum of 2 emails. At every stage of participation, you would get a max of 2 reminders of the next step needed to integrate into the community.

We've never actually had a complaint about our email reminders. I think most simply view it as part of the learning process to get acquainted with the community.