That is intetesting. Our district wants no one on social media. Apparently teachers start friending students and it goes downhill fast from there.
Your district would probably lose a lawsuit if they fired a teacher for having a social media account for personal use and not related to job activities.
My district has always decided to work with technology, rather than fight against it. We are NOT encouraged to friend our students on FB, and I do not. We are encouraged to let them follow us on Twitter, as long as we only use it as a professional resource, which is all I'm doing with it. We also let the kids freely bring their cell phones (no weird "phone jails", etc. like I keep seeing teachers brag about on FB, where students place their phones in "jail" at the beginning of class.) Our kids bring them, but aren't on them unless it's for an assignment (accessing the Internet, reading a book on it, etc.). In my class, I allow students to listen to music on their phones when they are writing. It keeps them quiet and on task writing.
You must be one of those "progressive" teachers. Welcome Back Mrs. Kotter. How do you know students aren't getting the answers fed to them on their phones?
Usually hashtags are not a part of clickable links. According the the info at the link I posted the use of hashtags can result in a 27% better clickthrough rate for your tweets vs tweets without hashtags. Significant when you are trying to get traffic to a website or get an ad read.