If you have lots of coins in your online bitcoin wallet,will posting that address in public like forums,facebook etc make it more vulnerable to hacking?
1.Should such addresses be kept secret as much as possible to keep them away from hackers eye?
2.If kept secret,is there a way for others to know how many wallet addresses holds big amount if bitcoins?
I think you wrong, as blockchains allows us to see other people transaction. With it wasnt without post bitcoin address, it still belongs to the public if blockchains let other people to see our transaction. If you mean do not publish private keys wallet, I would agree. Because with the private key other people can easily break into our wallet. And just advice, keep your private key on the paper or something other offline. Correct me if, Im wrong

thank you