Shelley Batts was threatened with legal action for posting a figure and a table from a scientific paper [When Fair Use Isn't Fair]. This is an important issue that's only going to get worse on science blogs. My own feeling is that it's fair use to post stuff from papers in the scientific literature as long as it is properly attributed.
One of the advantages of the online journals is that they specifically allow this. Here's the official word from the PLoS website.
Everything we publish is freely available online throughout the world, for you to read, download, copy, distribute, and use (with attribution) any way you wish. No permission required.If large corporations like John Wiley & Sons are going to threaten to sick lawyers on bloggers like Shelley then we'll just have to ignore everything that's published in their journals. That's what I'm going to do from now on.
[Hat Tip: Gene Expression]