Anything over a few hundred K deserves the benefit of the doubt.
If your service gets shut down after the acquisition that's not a good indicator that they bought the startup, that's an indicator that they bought you.
In a proper acquisition the team and the product matter, and the product will not normally be discarded after taking over (there are some exceptions to that, but this is not one of those by the looks of it).
In this case, the acquisition was for an undisclosed amount, the TC article guesses $6M but why is not detailed.
http://techcrunch.com/2010/10/08/google-confirms-acquisition...
So, I'm curious if plannr will be shut down or will be allowed to continue and develop.
The fact that "Having met at Stanford, Eidelson will be Product Manager and Prado will be Software Engineer of a new project they declined to mention at Google." does not bode well for plannr, after all with the two founders working on other stuff it might not survive for long.
Possibly a team of googlers will take over the running of the site or maybe it will be integrated in to other google services.