What I would do is counter with some reasonable offer to show you're willing to play ball for the reasons below.
IANAL but I seem to remember in my business law class that even if my last name was "macdonald" in US courts I would have trouble keeping "macdonalds.com" because of trademark issues. I imagine the same would be true for izillow.com. On top of which, as other posters have mentioned, their Terms of Service likely gives them the right to cut you off at any time. Your leverage is low.
For them it is a business decision where they would rather avoid legal expense and bad PR.
Keeping in mind that the lower of legal fees + PR damage or the dollar value in harm your app does to their brand and sales sets the upper bound for what they would likely pay.
If the site is getting about 2500 visitors a month, I would probably respond mentioning how much work and time you put into it, and emphasizing that you want to work with them on this, then ask for $4,000.
IANAL but I seem to remember in my business law class that even if my last name was "macdonald" in US courts I would have trouble keeping "macdonalds.com" because of trademark issues. I imagine the same would be true for izillow.com. On top of which, as other posters have mentioned, their Terms of Service likely gives them the right to cut you off at any time. Your leverage is low.
For them it is a business decision where they would rather avoid legal expense and bad PR.
Keeping in mind that the lower of legal fees + PR damage or the dollar value in harm your app does to their brand and sales sets the upper bound for what they would likely pay.
If the site is getting about 2500 visitors a month, I would probably respond mentioning how much work and time you put into it, and emphasizing that you want to work with them on this, then ask for $4,000.