[BrianOnHN]

Good additions. I'd like to add that these are all challenges that will be faced by all competitors of the existing model.

Personally, that's what lead me to focussing on what might be the most innovative direction I can fathom instead of the incremental direction (aka "this for that" innovation). If I didn't recognize that all of the challengers would face this same uphill battle, then I myself would've built "OKCupid for jobs" by now. It would 10X the pure-spam nature of the current market if the execution was done well, but current players are too big. To conclude, you have to outthink them and create something that can't be reproduced with effectively unlimited budget.