Connection #1: Botgirl
I discovered Botgirl via a “recommended follow” on Twitter. She had just posted a recent item about “What Does the Silent Majority of Second Life Think?” which got me interested so I replied and began to follow the thread.
Connection #2: Soleil
I discovered Soleil via an Is One Life Enough Song Contest entry. Our conversation was brief, as in Soleil sending me the MP3 file and my acknowledging it and Soleil acknowledging my acknowledging it. Of such brief, highly intentional exchanges, are many new connections made.
In both cases I would say the rationale for connection is “likely shared interest,” enabled by ability to communicate and follow-up online via communication media, i.e., social networking tools.