There are many non-traditional routes to get to know investors besides the usual networking events/cold email/calling. I'm friends with the author (Charlie) outside of just the tech world. We became friends a couple of years ago when he tweeted out about needed volunteers for a kayaking program he helped start over at the Brooklyn bridge park (http://www.bbpboathouse.org/ for anyone in NYC that's interested). I had grown up kayaking so was mostly interested in having way to do so in NYC, but also wanted to meet Charlie. When I showed up, there were probably 10 or so people from the NY tech scene that wanted to get some face time with Charlie and over the course of the day he spent 1-on-1 time with everyone. Most only showed up for that one session, but a few have been back from time to time.
This isn't a strategy that you can use to get access to every investor because like Charlie said, it takes time to build up relationships and really get to know people. However, if you do have a few key people you want to get to know, getting to know they outside of the tech scene can be a great way to build a long term relationship. You need to figure out a non-creepy way of doing so (i.e. don't just start showing up where they check in on foursquare (http://www.feld.com/wp/archives/2011/03/did-someone-ruin-fou...) but at the end of the day, investors are people and they often have causes/activities that they're passionate about and may overlap with your interest.
This isn't a strategy that you can use to get access to every investor because like Charlie said, it takes time to build up relationships and really get to know people. However, if you do have a few key people you want to get to know, getting to know they outside of the tech scene can be a great way to build a long term relationship. You need to figure out a non-creepy way of doing so (i.e. don't just start showing up where they check in on foursquare (http://www.feld.com/wp/archives/2011/03/did-someone-ruin-fou...) but at the end of the day, investors are people and they often have causes/activities that they're passionate about and may overlap with your interest.