Oddly, this phenomenon does not occur in older browsers, or at least in one older browser I still use. A Google image search for “lesbian daisy chain” will turn up radically different results in Opera 9.64 than it will in a modern browser.
If you search for “lesbian daisy chain porn”, the sexy stuff comes back on the newer browsers. The key is make your search explicit, no pun intended probably.
If Google stops serving up pron even when you ask for it specifically, that’s when it’s time for tar and feathers IMO…