The portrait that Airbnb paints of its hosts is homeowners who either want to occasionally rent out unused rooms, or people who just happen to have amazing weekend homes that they want to share with random strangers. That may be true for many Airbnb hosts, but there’s also a growing concern about so-called “mega hosts” who are effectively running hotel operations, renting out dozens, hundreds, sometimes more than 1,000, properties at any given time.

BuzzFeed News reports that Airbnb’s new tools that make it easier for commercial ventures like hotels and real estate companies, and their timeshare holders, to list and manage their properties on the site.

Travel researcher Phocuswright offers an estimate that 50% of property managers in the U.S. use Airbnb to rent their residences.

These managers range from small mom-and-pop operations to timeshare owners, and major hotels, and can offer anywhere from a few abodes to a few thousand.

For instance, BuzzFeed points to the profile of someone named Jan, who has more than 1,083 listings on Airbnb in locations ranging from Fiji to the Ozarks.

While Jan’s properties have mostly good reviews, some show that the rentals aren’t actually someone else’s home, but just a room in a hotel or resort.

In one listing, BuzzFeed notes, the guest said the residence was being run by Wyndham, a hotel and resort chain with more than 7,400 hotels around the world.

BuzzFeed News examined some of these properties and eventually contacted Wyndham Vacation Ownership, where a spokesperson confirmed that some of the listings were managed by one of the company’s timeshare owners.

“We have noticed owners opting to utilize their ownership to pursue speculative listings/advertisements,” the spokeswoman told BuzzFeed News.

Because these timeshare owners are able to rent properties at any of the company’s locations, they often list a wide range of rooms in a plethora of locations on the site. When someone books the room through, the timeshare owner does the same on their end, subbing their name for the new renter’s.

Profiles and listings similar to Jan’s are now popping up more and more on Airbnb. Inside Airbnb, an analytics tool, found more than 100 hosts with more than 100 listings each.

While an Airbnb spokesperson tells BuzzFeed News that the “overwhelming majority of hosts have one listing and occasionally share their space,” the other commercial listings — whether from timeshare owners or actual property managers — will account for an estimated $2.8 billion revenue each year.

Another mega host example comes in the form of TurnKey Vacation Rentals. Until a year ago, the online property management company, operated on Airbnb using profiles for property managers “Julie” and “Erica,” which had at least 1,000 properties listed on one account at some point.

While mega hosts may be growing in number and size, the phenomenon is not new to Airbnb. In 2014, a report from the New York state attorney general’s office found more than 100 hosts with at least 10 properties in the state. One particularly entrepreneurial host earned nearly $7 million from 272 unique Airbnb listings, all without paying the taxes that a hotel or inn operator would have to pay.

Even Airbnb’s own 2015 report of listings in New York City found that around 5% (888) of the city’s nearly 18,000 hosts had multiple unique listings on Airbnb.

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