Talk of Philly becoming New York's "sixth borough" is enough to make plenty of Philadelphians groan. The backlash appears to have killed off a recent transplant from Brooklyn: a flea market that opened here in June.

Brooklyn Flea co-founder Jonathan Butler remembers launching it. He says there was "a good mix of vendors and a lot of people and then as the summer wore on, fewer people came to the market and so fewer vendors did well and we sort of started to go into a gradual death spiral."

Butler admits a different location might have worked better than the Piazza in Northern Liberties, but there's something else he's heard about the market's demise: "All these people saying, 'Oh I'd never go to a market that had Brooklyn in the name.' And clearly we thought about that ahead of time, but I couldn't believe anybody would actually be that silly — that if there was a good market they would refuse to go because it had Brooklyn in the name."

The Brooklyn bitterness is no surprise to David Colon. He's an editor at the blog Brokelyn, whose motto is "living big on small change."

"I'm not 100 percent shocked," he said. "I'd have to say my biggest beef with Philly is sports-based, because I'm a Rangers fan and I'm a Mets fan."

Colon says he has visited Philly and was greeted warmly. (He once rode his bike to Philadelphia all the way from New York just for the experience.) On the NYC-Philly dispute, Colon says he doesn't think "it's a legit, terrible city-to-city beef," but he understands why some Philadelphians might be annoyed by all this sixth-borough business. "We wrote a thing, 'Is Philly the next Brooklyn?' And I can see — I mean, that kind of trampled all over the identity of Philadelphia — so I can see why people would be kind of annoyed by New Yorkers for thinking of it that way."

Colon says the new market may have also suffered because Philadelphia already has established flea markets and other spots for those seeking deals. Philly's last Brooklyn Flea was held last weekend.

Brooklyn Flea's Jonathan Butler says in his city, the business has done well, growing from one market in 2008 to five markets every weekend. This wasn't Butlers' first attempt to build a business in Philadelphia. He's also a creator of Brownstoner, the NYC real estate blog that failed in its Philadelphia expansion effort. When asked if he will ever try to replicate another New York project here, Butler said, "What's the George Bush saying? 'Fool me once, shame on you. Fool me twice, shame on me.'"

He points out other New York business ventures have failed to take hold in the City of Brotherly Love. "When we were deciding to go down there, Third Ward [the co-working space] was getting ready to open their location in Philadelphia, which has now sort of spectacularly bombed and taken the whole company down with it," he said."And that was going to be seven or eight blocks from there."

As for Philadelphians' feelings about their trendy neighbor to the north, Butler's calling for a ceasefire in the NYC-Philly madness. "The hostility toward New Yorkers from Philly seems so strange," he said. "Like, I don't understand why we can't all just get along."

He says he came south to Philly with the best of intentions. "We went down there because we really liked the city, and we didn't think there was anything arrogant about our coming down there, and we just wanted to make a nice market down there. And so it's sort of strange to be met with all this hostility just because we're from Brooklyn."

Just to be safe, Butler says for Brooklyn Flea's expansion to Washington, D.C., he intentionally left "Brooklyn" out of the name. It's called "The District Flea."