I guess a first world problem for me would be the way private messaging works on Twitter. I wish there was a way to have a private group messaging feature. I find myself having to screen cap a conversation back and forth between recipients.
If your service explodes somehow, you'll easily end up at 75,000 users with the stress that your product will die as user 100,001 will not be able to join.
Also, you need to determine whether your problem is either "a proper product" or just a "feature request".
In the case of the above, it seems like just a feature request.
I want to build a product, something useful.