The Tsukiji Fish Market had been closed to tourists for several months but now recently sections of the market have been reopened to tourists. The official reason for the original closure was due to the busy year-end trade.
However, Japanese media had been reporting that the real reason was due to tourists getting in the way and not following the rules. "Bad Manners" by foreign tourists mainly. This problem apparently had been growing recently due to the increasing popularity of the market as a tourist attraction, especially for foreigners.
Some fish traders had long complained of the tourist disruptions. I have never visited Tsukiji but have known of it for a long time. I was always surprised that tourists were ever allowed to wander around the market.
The MSNBC article has a link to a video of a visitor to the market licking a very expensive tuna before it was sold at auction. Apparently this being the final bad incident that led to the closure.
Now that the market is open again to visitors, precautions have been taken including etiquette flyer's and security guards during the auction. Some are very happy of the return of the visitors however, including owners of the many small counter-only restaurants such as Oedo.
So, remember, when visiting Tsukiji. DON'T KISS THE FISH.