I know that some people lament death by Powerpoint, but I find a speaker's slides generally valuable as both a listener and a speaker. Yes, many people (including me!) could do better with slides, but I find them useful. As a speaker, they help me keep track of everything I want to say, and drive home some points with visuals or reference lists. As a listener, I can keep track of what is being talked about, pursue any references I might be interested in further, and view graphics that often bring home points that words (especially spoken-only) do not.
My general practice when giving a talk is to post a PDF of my slides to my Web site, often with a list of references cited in the talk, and then tweet out a link to the PDF. I also send the PDF to the sponsor of my talk for distribution to those attending. That way, those listening to me do not need to be snapping pictures with their phones or writing things on the slides down when they want to remember something on one of my slides.
Based on my practices, I find it frustrating when speakers do not share their slides. Sometimes they provide them later, which is still far from ideal, but some speakers never provide them at all. When these happen, you see many listeners in the room taking pictures of slides they want to remember.
It would be much easier if all speakers would share at least a PDF of their slides right at the start of their talks. There really cannot be anything so proprietary, especially in an academic talk, that cannot be shared when those in the audience are snapping pictures and, as is sometimes the case, posting the photos to social media.
I hope that speakers I will be listening to in the future will adopt this advice. I certainly plan to keep my present practice in this regard.