Bruce Allen suggests that three follow-ups from an event are a lot better than none and I'd have to agree. He says:
One event = one email, one note, one call.
With the best intentions in mind, writing handwritten notes to everyone you've met is a great idea. But it can seem like a monumental undertaking so what happens? Days go by...then weeks...pretty soon months...and then it's a year. No follow-ups made. I hate to admit it, but I've done this, too (sssshhhh).
Bruce, on his blog Marketing Catalyst, suggests this, instead:
Sort through the stack of business cards and select three. Hang on to those three cards and toss the rest into a corner to gather dust (or hand them off to get entered in a database or whatever -- just get them off your desk).
Email one, write a quick note to another, and call the third. You're done. I'd say this can easily be done in about 5 minutes.
This approach makes sense. Sure it would be optimal to follow up with everyone. But because three is better than none, which is what we end up with most of the time, then three sounds great to me.
Bruce's post is #7 in a series of posts on tips for networking at an event. These are excellent bits of advice! Check out the whole series starting at post #1.