If not a secret, how are you marketing it?
I have a question - how can you afford to run this? I looked at the server costs on google compute and runpod.io, and the ones with GPUs powerful enough to run SD are pretty expensive. I'm guessing you don't have a lot of paying users at the beginning, so I don't think you have enough revenue to cover the costs (at least when you're just getting started).
Do you just spend a lot of money to fund this, and hope that once you have enough users it will pay for itself? Or did you find some affordable way to run a server? If yes, and if it's not a secret - where are you renting the server, what are its specs, and how much does it cost?
The only secret to making it affordable is to autoscale based on a current image generation traffic. It runs on a mix of Tesla V100 and RTX 3090 from runpod.io vast.ai and Lambda Labs.
I actually went through a couple of iterations with it, starting as completely free service, then offering one time payments for image credits and now settled on subscriptions as I see there is a demand for the product. Especially AI Editor[1] which I think offers a unique value to the users.
If you need a sign-in, e.g. to prevent abuse, you could start by explaining that a sign-in is required and why. At least then people won't be angry when they are ambushed by it
Saying that it requires login before someone spends time to think up a description for an image would have been nice (because I won't sign-in to try something anyways).
Edit: rephrased to remove overly negative language.
And labeling a domain as disposable, when it's clearly isn't, sounds a bit strange to me.
I use email verification API for this. It states to make decisions based on public email blacklists and lists of disposable emails. Cleary it's not perfect