How should one compare a refereed publication in SCIENCE to a blog on the web? In the debate over arsenic-associated bacteria can one really prefer Rosie Redfield's blog over Felisa Wolfe-Simon, et al's journal article? It seems to me that one should prefer the position that has the stronger arguments and/or greater experimental evidence. When a paper appears in SCIENCE that makes it more likely that its arguments are probably sound (as opposed to some random web post) but in the end it is only the arguments and evidence that counts for anything.
If you're out looking for solid research you will find it more frequently in SCIENCE and less frequently on the web. But any given paper (or blog or idea) must be judged on its own merit.
On the subject of alternate forms of life: I believe that mechanical life is far more important to consider as opposed to the simple substitution of arsenic for phosphorus in DNA.
When a search returns a large number of hits it would be good practice to restrict your attention to refereed works. When a search returns few hits you don't have that luxury and will have to study what you have.