Yes, it is very possible if someone has an active mouth lesion and sheds virual particles with saliva on that joint. It's even possible without active, visible lesions. HSVI and II viruses are longer-lasting than was originally believed. If you're smoking with someone who has a big herpes lesion, well, get yourself a cigarette/joint holder of some kind. Or if you're determined to smoke socially, make sure Mr. or Ms. Lesion Lips has his/her own joint.