My answer: I don't know that it is necessarily important or essential for students to use Slideshare, but I do see a few advantages to the program.
- You can share your presentation with others on a website instead of just through e-mail.
- You can do voice over instead of just having the audience read your slides/notes.
- You can search, view, and download others' slideshows.
- You can embed your slideshow onto your blog and other websites.
I'm not sure about high school as it has been a while since I was in it, but I know in college, slideshow presentations were a requirement for many of my courses. If students are able to practice making slideshows, they will be able to work on their presentation skills, something that will only help them later in life when they have a job.
As a teacher, this program is beneficial for the same reasons I listed for students. If students are absent, they can download your slideshow and listen to your presentation instead of just asking someone for the notes. I think a lot of the teachers who attend professional developments would find this useful to look at after the presentation to review the key concepts.