You need two pieces of information to access a Venmo account. The first piece of information is a username, phone number, or email address (any of them can be used). The second piece of information is a password. So is sharing your Venmo username on social media safe?
As long as you have a long, strong password that you don’t share with anyone, then sharing your Venmo username online is perfectly safe and poses no hacking risk to your Venmo account. In fact, you have to share your Venmo username or a linked phone number or email address in order for anyone to ever send you a payment.
HOWEVER, the same information that is needed by someone to send you a payment can also be used by someone to request a payment, so make sure you know that any payment request you receive is from someone you actually know before paying it.