Although I'm no longer in the dating scene. I believe the biggest challenge for most people is being patient enough to truly get to know someone before deciding to become "exclusive". What normally happens is both people tend to do their best to "impress" a new person they are attracted to.
This leads them to say "yes" to things they will eventually say "no" to once there is an "emotional investment". A couple of examples would be a girl who hates sports goes out on a date to a hockey game or a guy who has no interest in theatre goes to see a musical. The primary reasons are this is someone they think is "hot" and they don't want to "blow" the opportunity to get to know them by saying "no".
I suppose it's human nature to place more value on things and people who are "new" than those things and people who are "tried and true". However because people hesitate in revealing their "authentic selves" we often later here "He/She is not the same person I fell in love with".
The truth is we don't get to "know" each other until after the "infatuation phase". Awhile back I wrote a hub, "Do we save our best for (the beginning)...?" (Finding someone who will be themself from the start would save a lot of time.)