I don't buy your innocence here. I've been leasing houses for ~10 years now during and after college. The leases have always required a mix of landlord approval for subletting, banned running a business from the house, and prohibited occupation by non-lessees.
Here are two clauses from an older lease[1] I happen to have in my desk:
* Tenant shall not assign this Agreement, or sub-let or grant any license to use the Premises or any part thereof without prior written consent of Landlord.
* The premises shall be used and occupied by Tenant and Tenant's immediate family... exclusively, as a private single family dwelling.
Your faux innocence is pretty annoying actually. You were abusing the property for commercial purposes and you're surprised he didn't give you a friendly phone call?
1 Looks like the lease was originally snatched from www.academichomes.com/downloads/ExampleLeaseAgreement2.doc
OP would be 'abusing' the property if he were running a crack den. I see no problem with tenants doing whatever they want with the property that they are leasing - as long as no damage is done & neighbors are not troubled.
That's why landlords define "damage [being] done" and "neighbors [being] troubled" in a legally binding contract called a lease, and when you break that contract, you can get evicted.
I strongly suspect most resistance to these basic facts in this thread is typical Airbnb/pg/HN apologia. It certainly isn't coming from anyone who has rented in NYC, that's for sure.
I don't find it that hard to believe that someone would blindly sign a lease after only quickly skimming over the important bits and then never look at it again. I remember one landlord looking quite surprised when I sat in his office and read all 8 pages of the contract, asked for clarifications on a couple of points and asked for one clause to be changed. It seemed to me that she'd never seen anybody do that before.
When said person is making a fulltime income solely from renting space in an apartment that he is only leasing, well, "most people" would think "I should probably take a look at my lease first"...
I don't find that hard to believe either.
What I find revolting is someone not reading the lease, violating it, then playing the victim.
Now that you were cranking tons of guests through for personal gain, you were surprised when your landlord took exception. If I found out that somebody was blatantly disregarding the rental agreement they'd signed with me for commercial gain, they would not be getting a friendly "hey brother, can you please stop?" phone call either.