I fully agree with the parent.
In this instance you seem vulnerable to a flip. They will lock you up with and exclusive "marketing period" then sell an exclusive license to Google (Youtube) or Vimeo in an afternoon, and go looking for their next victim. You could probably get a higher price if you took longer to negotiate, and not share a cut with them. If you refuse the deal they make, you will forever be blocked from selling to "their" buyer.
Some of my best friends are in this business. Some of them are ethical. They all love money more than technology.