I've been playing around quite a bit lately with Riya lately (and Riya-like technology). In fact, they've just released an API, and I'm in the process of creating a .NET library (like Flicker.NET) to access the service.
Anyway, since I've been playing with Riya, I've really been nothing but impressed with it. One thing that does continually bother me however, is the quality of the thumbnails that they generate.
Take this picture of Damgaard & Josh...
Riya generates this thumbnail:
Notice how grainy it is, especially on the edges! In my opinion, it's pretty painfull to look at.
Now, take the same picture resized using bicubic resize:
Much better! The lines are MUCH smoother, and the picture is actually distinguishable. Check out http://www.interpolatethis.com/closeups/nearestCU.html for some additional information on the different interpolation techniques generally used.
Maybe it's just an "alpha" thing... Either way, I've added this as an issue to the Wishlist Wiki