It might cause unnecessary awkwardness to those who happen to read it.
Accumulating accidental peep readers cos your friend don't really have intention to read it....sore eyes.
People might vomit blood from your too much cheesy lines which was NOT beautifully written *i hereby accept those who know how to write simple words yet able to touch my soul(original ok, not copy paste from some quotes)*
PS: Someone who have blood relation to me just did that. I understand young love but they should know the invisible line. Duhhhhhhh......