You don't need terraforming for a self-replicating AI to take root in a galaxy and convert the galaxy into useful stuff.
I don't think gathering information about whether or not a solar system is populated will be significantly more expensive then colonizing it.
So you're saying that people will send self-replicating AIs to convert galaxies into useful stuff without paying attention to what is already there?
That doesn't seem at all likely to me. The AI will probably pay attention even if you don't explicitly program it to do so.
If it's worth saying, but not worth its own post, then it goes here.
Notes for future OT posters:
1. Please add the 'open_thread' tag.
2. Check if there is an active Open Thread before posting a new one. (Immediately before; refresh the list-of-threads page before posting.)
3. Open Threads should start on Monday, and end on Sunday.
4. Unflag the two options "Notify me of new top level comments on this article" and "