A lot of conferences are poorly run and are a waste of time. The conferences I find that I enjoy the most (and I go to a lot by way of my job) are the ones where the topic attracts the kind of people I find interesting. The people are always more valuable than the content. I have yet to attend a conference I've enjoyed where this wasn't the case.

It also depends a lot on where you are with your career. If you're new to things, meeting new people and learning new things will have more appeal to you. If you've got an established network and aren't in a hardcore learning mode, you'll probably be disappointed by most of them.

Agreed. Small, focused local meetups, however, I've found useful much more frequently and should not be lumped together with said conferences.

Yeah, most are, but the good ones are amazing. As a for instance, I spent years going to large corporate oriented industry conferences, and hating them. Last few years, I've discovered the smaller, community run Python conferences, which have had a transformational effect on myself and my understanding and my career.

That's why something like Lanyrd is great, for helping you find those small events which are full of smart passionate people doing cool things.