Facebook already updates their API and policies very regularly, nothing they give an application access to can be given for granted in the long term. Especially when it deals with private content.
When your service is dependent on another, you're always at the mercy of an update that can shut down the API feature you were using, whether the intention is to kill your service or not.
In this case it seems like the goal of the website is to become a starting point for a person's browsing/searching experience, facebook and google want the same thing. If they feel threatened they could cut just stop Greplin in particular from accessing their API. It's not hard for them to update their API terms of service to make that kind of use forbidden, for instance. That kind of tactic has been used in the past.
That's why I see a lot of uncertainty in the future of that service. I'm not worried about the founder and the company, though, their most likely exit is a talent acquisition by Facebook or Google.
Yes, but you haven't really address 'why' they would do it.
> In this case it seems like the goal of the website is to become a starting point for a person's browsing/searching experience, facebook and google want the same thing.
This is your only 'why', but it's very weak. Every company wants to be the 'starting point for a persons browsing experience', but Facebook doesn't provide that, and neither does Greplin. Google does of course, but Greplin doesn't.
Your point reduces to "companies which consume APIs might compete with the companies which create them, and so might be shut down". Of course, your statement is true, but it's valueless.
The companies providing the APIs don't have to justify the "why". When I was working on Facebook applications a few years ago they would change the API calls and rules almost monthly, app developers had to adapt or die. The changes were often due to apps abusing the system in one way or another, but Facebook defined what was abuse or not. Sometimes the changes just looked completely arbitrary and sometimes meant that some applications were just not possible anymore due to vanishing API calls.
Exporting the private data from Facebook is considered a big no-no, from what I remember the TOS might only allow you to do so for a short period. Maybe that search service gets away with it because it stores an index based on the private data and not the private data itself. If Facebook gets uneasy with how close the index is to the original data or what private information leak might happen if Greplin is compromised, that could be a good enough reason to put a stop to it. Facebook not getting into a private information leakage scandal is probably more important than allowing a startup to live on Facebook data.
When your service is dependent on another, you're always at the mercy of an update that can shut down the API feature you were using, whether the intention is to kill your service or not.
In this case it seems like the goal of the website is to become a starting point for a person's browsing/searching experience, facebook and google want the same thing. If they feel threatened they could cut just stop Greplin in particular from accessing their API. It's not hard for them to update their API terms of service to make that kind of use forbidden, for instance. That kind of tactic has been used in the past.
That's why I see a lot of uncertainty in the future of that service. I'm not worried about the founder and the company, though, their most likely exit is a talent acquisition by Facebook or Google.