Most answers here can be rated on a scale of best to worst:
Best: Here are the steps to solve this problem, the answer to this particular problem, the notes on how to carry out each step, why you should do it that way, and what might go wrong during the process and what you can try if that does go wrong.
Better: These are the steps I took to solve this problem that can be generalized to solve similar problems for other researchers.
Adequate: Here is your answer (copied from my family tree with sources and working shown).
Worse: Here is your answer from my family tree (no sources or working).
Worst: Contact me; I have the answer.
Contact-me-privately answers fall into the "worst" category. Like the well-used proverb, "Give a man a fish and you feed him for a day. Teach a man to fish and you feed him for a lifetime", these answers only help temporarily. The OP has his answer, but doesn't know how to find a similar answer again. However, when the answer is worked up the scale to the "best" category, it teaches the OP to find similar answers and he "eats for a lifetime".
On Genealogy.SE, when users ask questions, they get their answer and future visitors can (should be able to) also read and learn. However, this doesn't work the same when the answer is given privately. The OP benefits from it, but no one else does. So, these are obviously a problem. Why visit a site where existing posts don't help you at all?
These answers are not a good fit for a Q&A site. They are non-answers, really because the post itself does not answer the question, even if the private message does. Think of it as a link only answer. Eventually, the link will rot and the answer will be of no use to anyone. This is the same (but worse). The answer is useless to everyone but the OP from the moment it is posted.
For these reasons, contact-me-privately answers are deleted
and converted to comments. Per Robert's comment here,
Solicitations for personal contact is not permitted in answers or comments. The public nature of these sites specifically dissuades that type of private, off-line contact. That is by design. We do not provide social networking functions that would allow you to contact a user privately, so if a user wants to be contacted in this manner, they can leave that information their profile. Chat would also be appropriate because it designed to be a bit more social, and it is not really considered part of the Q&A canon.
These contact-me-privately answers will be deleted without conversion to comment in keeping with the nature of SE. They don't help the community or visitors at all and they don't help the OP beyond giving him the facts. So, remember to "teach the OP to fish" (metaphorically speaking) rather than to give him a fish.
No-work-shown answers fall into the "worse" category. They are a little better, but they're still bad. The basic problem with these is the same: the OP gets his dinner, but will eventually starve because he doesn't know how to fish. These have the same solution: show your work. How did you find the date of birth? A birth certificate? An obituary? A draft registration? Again, bring it to the "best" category. Show the OP how you arrived at the answer, what could have gone wrong and what to do if it had gone wrong, and why you chose to use that particular method.
Because these answers make no attempt at helping the OP learn how to get answers for himself, they don't really help more than giving a fish helps. They are not useful and should be downvoted. If the answerer does not edit to show his methods after a reasonably long period, the answer will be deleted.