An attention-seeker who compulsively, addictively blogs or posts to a social networking site many times a day.
Sarah's a postaholic. Six, seven times a day she pathetically pukes out where she is, what she's eating, what she's watching on TV. Who gives a flying fork?
A person that has been warned or advised NOT to post their picture on Facebook or other social media EVERY SINGLE DAY. The person then goes on to post ANYTHING, whether relevant or not, every single day.
"That girl from high school stopped her "selfie" posts, but posted a picture of her flat tire...She is such a postaholic."