The Bais Shmuel (YD 51:8) says that there is a Cheirem from the Ge’onim.
Wolfish,
You have kashas on Hagoen HaRav Shternbuch? You disagree with Hagoen HaRav Shternbuch? What do you want from me? I’m sure you are either 1) a gaon on Rav Shternbuch’s level or 2) have unquoted sources that disagree. If the latter, please quote your sources. If the former, I tip my hat to you.
I am completely floored that you find it appropriate to compare the seriousness of (C’V) breaking a shidduch to that of buying a house. Breaking a shidduch involves serious halachic consequences, as mentioned above, and requires a shaila (especially if it is not mutual) if it is allowed in the circumstance. It is NOT always permissible. Divorce is also not always permissible.