Name calling: Repeat names in a fictional world

I once came across some article (or plotting device, I'm not sure) that stated I should get rid of any similar names among my characters. Strange, eh? Especially when, if you want a story to sound authentic, you're bound to have some anomalies, right?

What got me thinking about this was my re-write project. I've tried not to have the same names run through my work as I go, for no real reason other than to just not repeat the name. Unless it's a character cross over, which I love seeing in books as well as doing myself, I dodged repeats like an agile gym student. After writing so many modern based novels, though, common names start to run thin, and repeaters are popping up. Which got me thinking, wouldn't that make it more authentic?

Writing fantasy allowed me to have some really fun, strange, and out-there names. I could call a character Dagmar because it means "glorious" and she was a glorious warrior (or stage performer). I could name them Lucasta, Artimus, Checks, or any number of things because it simply didn't matter. They were in a fantasy world, 'normal' was a different state of mind.

Looking at the modern world is different, I think that repeat names would land more authenticity. Example? My graduating class contained 3 Megans (of various spelling), 4 Ashleys (Again, various) 4 Jeffs, and a multitude of other repeats. And that was one graduating class, the rest of the high school was littered with them. I'm sure you know more than one person of a same name, so why shouldn't your characters?

No, seriously, why shouldn't they?

I'd love to know your opinions on the topic, so please share them.