Lots of unique and optimized text is good for ranking a page, that's clear. But sometimes this text is 'too much' for the readers. Aiming at a 800 word text for a product page for example raises the question where to put all the text because not many surfers will read it all anyway.
So we show about 50% of the texts and hide the rest with
<div id="r" style="display:none">bla bla bla</div>
When the surfer is interested, he can open the rest of the text with a click - it pops down the text that is hidden with style=display:none.
I consider this a very useful and good way to present the content to the surfers and they appreciate it. There is nothing spammy involved as I am not trying to stuff keywords or game Google anyhow.
But how does Google see and valuete this? Is the 50% of the text that is hidden on load of the page 'lost and worthless' no matter if it's unique and great content? Or will Google give weight/value to this text as if it's visible right away? The text is always in the HTML of the page, it's just not shown by default, only after the surfer clicked on 'read more'.