I'm sure that, like me, you've seen people give speeches by reading from a page. They usually start by making eye contact with the audience and occasionally glancing down at their notes.
Soon enough this gets reversed and the audience ends up being treated to occasional glances as the speaker (or reader) ends up just flat out reading everything from his notes without bothering to draw the audience in.
So instead of ending up listening to a speech, you feel like you're back in the book club listening to a reading from some high-profile author.
Good speeches are presented, not read. And good speakers engage, they don't recite.
Anyone who wants to grow into a authoritative public speaker, and wants to be giving great presentations on a regular basis, has to avoid the temptation of reading their speeches, but instead cultivate the skills to present their material with vigor, passion and authority.
Now there are a group of highly-paid think tanks who, in spite of their usual lack of fashion sense, are allowed to read their speeches. And they're called academics.
The norm for presenting research papers in an academic setting is not to 'present' it in any possible exciting sense of the word, but simply to read it, usually without too much emotion.
Now, I've had professors admit to me the irony of flying to Vienna to hear world-experts read their papers, when in fact they find it quite boring and would rather go listen to the boys choir.
But academics are allowed to read their papers, since the power of their presentations usually lies solely in the content of their papers, and not their presentation (and thankfully not their dress code, just kidding!).
Chances are though, that you're not an academic, and that your audience is not going to fly to Vienna to hear you speaking on biochemical plasma microfusion. So you should probably not read your speech from a piece of paper.
This is why, in my opinion, its safe to work from a set of concise notes - consisting of key words and trigger phrases, instead of a fully written out speech.
Speeches that are fully written out are tricky, because they'll invariably tempt you to start reading from them. This is especially true if you're not all that comfortable with your material, haven't rehearsed it well enough and easily lose your train of thought.
In these cases it's good to know that you can always fall back on the good old paper version which has everything you need to say, word-for-word, right there in black on white.
Any public speaker interested in giving great presentations, need to learn the art of audience engagement. And the one sure way to NOT engage your audience and keep them captivated, is to follow the snore-inducing habit that some speakers can't seem to shake: Reading a speech word for word...
Now of course, there are many brilliant public speakers who use fully written out speeches. Politicians, though not always great speakers, almost always do, since they have speechwriters who put the pen to paper for them (See this copy of Barrack Obama's healthcare speech on the right, after his re-write, for the reason why speechwriters need an incredibly high self-esteem!).
So when it comes to notes, there's no absolute, hard-and-fast rule.
My experience has been though, that especially newer public speakers will play it safe by using concise notes instead of fully written out speeches:
1) It's fine to start with a fully written out speech to help you solidify your content.
2) Then rework it into a summary using bullet points with key sentences and trigger phrases on your notes
3) Now rehearse your material using only these notes
4) After rehearsal you can always go back to your fully written out speech to ensure you didn't miss anything.
This process has worked well for me for many years, but just because I personally ascribe to it, doesn't mean you have to. Whatever works for you, and will help you with giving great presentations, which means it doesn't end up with you reading your speech for a piece of paper, is just fine.