I was thinking of implementing this effect on my site where the text appears whenever the user scrolls down.
Here's some examples:
I wanted to know if this is bad for SEO since the text appears whenever the user scrolls down.
As long as the content is available in the actual HTML, I wouldn't think such an effect would have an impact on SEO. The pages are a bit slow to load, though, which does apparantly influence Google.
More and more people scoff at this, but if you turn off JS on these sites, you see no content at all. I don't care what anyone says—that's totally unnecessary and really poor practice.
For SEO content matters. If you get more of content ti will help in seo. If you want your mobile site as well then you need to change your layout for that. Good luck!
If you get content by demand (like - "se more" => ajax request), the crawler will only see your initial content, without the one loaded after the request.
In both of your cases there are no AJAX requests so, the SEO should not be affected (if you run the page with no CSS and no JS, the content is there).
In case you want to approach this kind of UX, get a plugin (or create one) that handles "in page" elements.
The "by demand" requests can be used for images, where you can also show a nice "Loading"
When I look at it I feel that your sites are a little bit too playful and it is very important for you to have the best design but that might lead to the fact that some people have problems with actually finding your content pages because they can't find a decent reliably structure. The same could be true for the search engine spiders.
You can use them but you have to be focused on the content of your website. If it is well structured and have the relevant content then there is nothing in your website regarding SEO. You have to fix that whether you want your site only in mobile or in system and mobile this affects most.
Content might be the king however User Experience is the Queen for google.
Flash is not good for SEO. Search engines cannot read / crawl flash objects.