And why not?

Many Life-Bearing Planets Could Exist In Interstellar Space

Long ago in a solar system not at all far away, there could have existed about five to 10 Earth-like planets in Jupiter-crossing orbits. These planets today could harbor life somewhere in interstellar space, according to a planetary scientist at the California Institute of Technology. In the July 1 issue of the journal Nature, Caltech professor Dave Stevenson says in a new study that such objects could be life-sustaining due especially to the molecular hydrogen they accreted when the solar system formed long ago. Called "interstellar planets" because they would exist between the stars but no longer in orbit around an original parent star ...

Elsewhere in the article, Mr. Tindol gets a little too free with his theorizing about the possiblity of evolved life. Personally, I think these have far more potential as terraformable human colonies. You'd have to use geothermal energy for power and (perhaps) collimated starlight for light but it ought to be doable when interstellar von neumanns come into play.

First, we'd have to find them though.