It's a nightmare for any guy, but the current statistic of fathers who have unknowingly raised a child that isn't their own is between 5 and 15%. Even if we're generous and say it's 7.5%, with a US population of men who are fathers at over 70.1 million. That's still 532,500 fathers raising another mans child unknowingly.
That 70.1 population statistic is as of 2008, which is the most current available population consensus for fathers ( www.census.gov/newsroom/releases/archives/facts_for_features_special_editions/cb12-ff11.html ). So the number of men raising someone else's child is well past 532,500 by this point.
Personally, I think that 1% is enough of a reason to make this change and have hospitals require paternity test as a required procedure involved with the rest for each visit. The price of delivery is currently at $3,500 in the US. If you throw in prenatal, delivery-related and post-partum healthcare, and you're looking at an $8,802 for total medical costs today. A legal DNA paternity test only costs between $300 and $500. Considering how expensive this whole ordeal is, an additional 300 - 500 is really not much at all. So $9,102 to $9,302 instead of $8,802.
The doctor's could handle the procedure and only notify the family if the test comes back showing he's not the father, so as not to be a nuisance for the majority of families. But the 5 to 15% of fathers will be spared from getting screwed over.
I'm not some paranoid dude lol