During working on an index migration script we found out that the SearchQuery of the search service is limited to 20 result items by default. I'm pretty sure that some parts of the code (at least update event handlers) are using the SearchQuery with the assumption everything is returned. So this needs to be checked or the default limit needs to be adapted.
Limiting the result set does not make any sense. Even not for protection reasons. If someone wants to paralyze the system that can be easily done by setting the limit to a high value.
Merged into 1.4.x with rev 15168.