I've had a bit different luck. A few have paid for flights and hotel, some included a honorarium of some sort but most were paid on my own dime outside the free pass.
Two of my recent good friends are fellow speakers I met at conferences abroad. I met them abroad first but they live about 40 miles from me in the States. A couple days abroad felt like we were condensing months of friendship.
Just an alternative point of view, IMHO: if talking at conferences is tough, you should try writing papers to get published in IEEE/ACM conferences. After going through revisions and getting them approved by your academic adviser. ;)
I'm so glad I left academia behind and work in industry now. I've presented at a few conferences and enjoy it every time. Its actually fun compared to publishing papers at research conferences. But that's just my personal point of view.
Interesting… I've never really thought that the point of speaking is to get a message out to the maximum number of people — which seems to be the definition of effectiveness the OP is using (and on that scale I wonder why books are at the bottom too…)
Some of the reasons I speak at conferences:
* Before I started speaking at conferences I got a lot out of attending. Both in learning and networking. As corny as it sounds I like to give a little back to the communities that helped me when I was younger and less experienced.
* Not everybody learns the same way. I know that I've attended workshops and talks that have made clear topics that I've found opaque after reading books, blog posts, etc. People have told me that they've got more from one of my workshops than they have from hours of reading and unstructured practice. So while I might not be reaching the maximum number of potential listeners, I may well be reaching people that I would have otherwise missed.
* I reach people through different channels. The people attending a conference are not necessarily the same people who read blog posts, mailing lists, etc. If you're following a blog on X, then you're interested in X. Conference talks are an opportunity to reach people who maybe didn't even know X existed.
* I find presenting in front of groups a little daunting and difficult. Practice has made it less daunting and easier. Communicating to groups of people is a useful life skill — from business meetings through to pitching to investors. Presenting makes me practice and improve it.
* I value the time I invest into making a good presentation. It forces me to put my thoughts in order and really think about the most effective way of communicating a topic.
* Unlike the OP I have got work through speaking. Both directly, from people who've seen my speak, and indirectly from folk googling around a subject area and finding my name pop up repeatedly around particular topics at conferences.
* I generally don't present at a conference unless I get at least travel / accommodation / ticket. So this reduces the cost of an event to opportunity cost at worst. This means I can go to more events. I enjoy and get value from conferences so this is a good thing in-of-itself for me.
* Speakers usually hang out together at some point. This means I've had the opportunity to meet and occasionally make friends with some wicked smart people. Occasionally folk in the "Squeee! I'm a fanboy" area ;-)
* I generally get more feedback from a presentation than I get from a blog post. Both directly from talk Q&A, folk approaching me with specific questions, etc. And indirectly from watching the reactions of the audience during the session.
* You often have the opportunity to present something multiple times at different events. This allows you to experiment with different ways of putting the message across with fresh audiences. Something much harder to do with blog posts, etc.
Two of my recent good friends are fellow speakers I met at conferences abroad. I met them abroad first but they live about 40 miles from me in the States. A couple days abroad felt like we were condensing months of friendship.