Here is the photo I dragged into MacJournal from my desktop, and had Macjournal upload it to Picasa while posting this entry:
Now, compare the resolution of that photo with the actual photo on Picasa - to show this here, I am editing this post via the LJ web editing window, and using the Picasa generated "embed photo" links for "medium" and then a "large" size photo. I am sure you will be able to see how these images are much higher resolution than the original!!: