Is it safe to add yahoo question and answer to twitter or any other account .......?

That depends on what type you are , i mean friendly or rserved or privacy liker . while there is nothing big deal in connecting your answers account to twitter or facebook , yet its another way to show to your friends how active you are in online . one of the main benefits of adding your account to twitter or face book is that , you can set animated gif avatar to your profile . many are using only for that purpose , including me ! lastly if you are too concerned about your privacy and doesn't like to share your activities with others then don't do that . There is nothing harm in doing that . you can proceed if you have many friends in fb and twitter , who knows after seeing that , they may also join this site !

Regret. Thanks

It depends on what you are comfortable with, if you are okay with all of your Twitter followers or Facebook friends knowing who you are on Answers and seeing all of your Q&A then it should be safe.