I do also. But those that I have never met often are extensions of my "base" network who I have met face to face and created a trusting working relationship with. I may have people in my network who I work with who are friends of friends that I have never met, but they are connected through one of the core groups (think linkedin 2nd or 3rd degree. Few have NO connection). I also look at online conferences or interaction via video conferencing as a viable alternative to face to face interaction.