Parse is a distraction for FB. You are not even in the same business. Regardless of what you say, you are unable to override the CEO if or when he decides that Parse is to be shut down. The alternatives are more appealing because their business model solely depends on customers paying for the back end service.

The best thing FB can do is to bind itself legally to continue to run Parse for the next x number of years.

If FB wants to dabble with PaaS, businesses are going to assess Parse on the basis that it is only an experiment. Tying oneself to a back end is like marriage. No one will invest in a relationship if the other side is only half serious.