They changed the background color. Ok. It is still quite obvious to me what is an ad and what isnt. Perhaps the old yellow was too subtle.. some people might not know that is an ad even if they switched back. What if they brought back the blink tag like:
Google made an aesthetic change to the sponsored ads back in July to better match the new look and feel they pushed back in may. Nothing to do with Google instant at all.
What's funny is if people are only noticing this now, then the ads are obviously totally ineffective.
<blink>AD!!!!</blink>