I'm curious if speakers (bloggers, google employees like Matt Cutts) get paid for speaking at conferences. If they do, how much? If they don't, or they get paid so little that it's as though they don't, why do it? What are the attractions beyond money that lead a developer into public speaking?
It varies. I have had speaking gigs where I spent my own money to get there, to eat, and so on, and didn't get paid to speak. I would say my norm for a conference where attendees pay is free admission, economy travel and hotel covered (but not meals, cab fare and the like), and possibly a small honorarium (eg $500 per talk.) For a conference where attendees do not pay there is no honorarium and often no travel covered either.
Some large conferences offer a few selected speakers a pre-conference which can pay a full week's billable rate or more for a single day (because, of course, you put a lot of time into preparing that day of training). I have heard of conferences that actually ask speakers to pay to get in the door in addition to covering their own travel expenses.
For me, the benefit of being there for the week and the benefit of being able to say "I've spoken at ten Tech Ed US, four Tech Ed Europe, and three Tech Ed Africa" (so far - fifth Tech Ed Europe is next month) is what has to balance against my time spent preparing the talks and being there. The honorarium rarely factors into it. (How much speaking do I do? http://www.gregcons.com/KateBlog/CategoryView.aspx?category=Speaking)
Depends on the conference, the speaker, and how badly you're wanted. 99% of the conferences I've spoken at have given free admission to speakers. Some have paid my travel and lodging, but not always.
Sadly, I'm seeing more and more conferences where, if you really want a speaking slot, your best bet is to become a sponsor -- aka "pay to play." For some reason, these also seem to also be some of the priciest conferences to attend. Consequently, when deciding which sessions I'm going to attend at conferences, I tend to cross off any that feature sponsored speakers, as they rarely say anything that isn't marketing-speak.
It sounds like you're wondering if you can make any kind of decent money speaking at conferences. The answer is "No, not just from that."
Typically the people who are able to make a living in writing/speaking/blogging are using the writing/speaking/blogging to attract attention and give credence to what they are making money at, such as consulting or teaching.
It depends on the conference. For most conferences, the conf registration is comp'd, but travel & hotel are the speakers responsibility. I know of some other conferences where speakers are also required to pay their own registration fees.
Keynote presenters are almost always paid (in addition to having their hotel and flight covered). Some conferences have a middle tier of "invited speakers" who may get a small stipend or have hotel and flight covered.
If there's a particular conference you're interested in, the web sites for most conferences list this information with the speaker submission information.