While there have been some reporting on the survey results, I don't think that many have focused on the "rest of the story", as Paul Harvey says.
The rest-of-the-story is not that 51% of the population is Protestant or that one-in-four (25%) presently describe themselves as Catholic, but that more than one-in-six American adults (16.1%) are presently not affiliated with any particular religious faith.
The Pew report went on to describe that this group of unaffiliated people are not primarily "secular" but rather, "nothing-in-particular". About half of this growing group of restless and unconnected adults often described themselves as "religious" but not connected.
If you realize that another 5-10% of those surveyed identified themselves with a particular religious group or denomination but readily admit that they frequent their house of worship rarely (maybe Easter or Christmas), we can gain a better understanding of what we normally call the "unchurched" in America. Based on the estimate of about 245 million adults in the United States, about 25% would be "unchurched" or about 61 million adults. This is more than the Pew Forum estimate of the total number of Evangelicals in the United States.
Americans remain some of the most religious and most diverse people in the world. Biblical Christianity continues to play a very prominent role in American public life and the Pew report found that Americans are very willing to experiment and to embrace a religious point of view other than the experience of their youth.
Reminds me of what Jesus says in John 4:35, "Do you not say, 'There are yet four months, and then comes the harvest '? Behold, I say to you, lift up your eyes and look on the fields, that they are white for harvest."