If users ask my personal contact for projects, can I give them in Stack Exchange?
Contact information is a fuzzy case. If the following appears in an answer or a comment (or even a question):
It's likely to get flagged and deleted.
I know because we get flags about it nearly daily.
If you want someone to contact you, refer them to your profile, and have that information in your profile.
You may be curious as to why this is the case.
We get a lot of users that like to say, "hey, email me answer @ ...." or "Hey, what's your IM to help me fix more problems?". That's not what Stack Overflow is meant for. We're meant to be a Q&A resource. We can't very well do that if the Qs and the As aren't here, can we?
If you're the lone hapless Googler, what would you rather come across: