Well unless google has specified that it is – then it’s not.
You have to remember that google spiders don’t look at your styling – because they don’t care how your site looks – they just see the raw HTML. Now as long as you play the game and follow their rules making the site’s hierarchy correctly and not spamming keywords it dosen’t matter.
If you hide things off your page with -9999px it is irrelevant because the google bot will SEE it on your page, as part of your main HTML content. So if you are trying to hide spam with -9999px it ain’t gonna work because, google sees the HTML not the rendered page.
So -9999px is irrelevant, it’s like trying to hide stuff with the same text colour as background – it dosen’t work with bot’s because they only see the HTML. So it is no "threat" to google.