Social Media Policy for this Academic

I am in the process of putting together my opening slides for Genetics this coming semester. One of the key pieces of information for students is the agreed upon lines of communication. I always prefer the school email because everyone has searchable access and it is a great way to lay down a documentation trail to avoid misunderstandings. However, there are exceptions and social media out there that can create confusion that could be clarified. For example, sometimes I need to give out my cell number to small groups of students working in the lab when I am elsewhere in the building (pushing flies, nothing dangerous) or if we are on a trip. I also get requests on social media occasionally. This can be fine for Twitter or LinkedIn, but not so fine for Facebook or when they attempt to contact me on my private email.  We all have our own preferences and level of comfort regarding how close to get with our students online so here is a table to clarify where I stand.