I think that we forget that it’s normal for people to come and go from our lives. Old friends lose touch. People go down different paths.
It’s interesting with the rise in popularity of social media it’s become a trend to “hoard” friendships. When it comes to meaningful relationships, quality is definitely greater than quantity.
Not to say that if you see someone you recognize you shouldn’t say hello. Just realize that it’s only awkward if you make it awkward.