You really never know when new business is going to come from old connections. NEVER burn bridges. Connect connect connect.
Example 1: I have done/am currently working on some promotional copy for Upper Canada College. Via that connection, another private school in Toronto pinged me and asked for some social media advice, so I spent the last few hours putting together a "shopping list" of choices for them. They've already dipped their toes in, but the potential is so much greater, they need more!
Example 2: I knew Ian Kelso from my days as editor of Silicon Valley NORTH back in 1993. Started connecting again last year when I was at GCI, and attended a few Interactive Ontario networking drinks. Got chatting to a Russian tech company about football (soccer to the locals). Anyway, lo and behold, got an e-mail out of the blue last week -- "We're launching a new venture, need some PR, thought of you." Cool. Had a brief Skype call to Russia a few hours ago and chatting more tomorrow.
Example 3. I worked at Beer.com a few years ago, and we featured an interview with an actress from a very famous film, although you wouldn't recognize her under all the special effects! Anyway, lo and behold part 2, I got a LinkedIn message today from her publicist -- she's starring in an upcoming horror series and they need to get the word out. So I am going to suggest some ideas there.
This all goes to show why it pays to make as many connections as you can, even if, at the time, it only seems if the other party is getting something out of it.