Saw this question on Hacker News today:
Went to a talk by a VC who is very active in my area. Didn't get a chance to introduce myself after the talk (there were < 25 ppl at the talk but the VC had to run). A few hours later, was out for drinks with a friend and saw he was at the same bar but talking with someone else. Discussion ensued with my buddies around whether or not I should intro myself considering I didn't have a chance earlier in the day, but I ultimately decided against it. What say you: Should I have? I ask for the next time I'm in this situation.
I say hell yes you should introduce yourself. But you should also respect that the VC is out with friends and probably isn't up for a long conversation.
I would suggest you walk up to the VC, say "I saw your talk today. It was great. My name is Jane Doe and I'd love to find a suitable time to tell you what I'm working on. I'll send you an email to follow up. It's a real pleasure to meet you." Then make a polite departure.
My view on these sorts of things is that I love meeting people, no matter where I am. But I don't love being pitched when I'm out with friends and family. The Gotham Gal has witnessed this so many times that she gets annoyed by it now. It happens most often at parties. Sometimes she'll just grab me and say "let's get out of here."
Social situations are ideal for a quick hello. Make an impression. Put a face to a name. But don't pitch. That's going overboard.