Unless people want to change the mongodb code that they would be using, using the agpl software should be a non issue and there are not problems with it. People should start understanding the available licenses instead of spreading fear.
I know that multiple other companies have a similar policy (either a complete ban on using AGPL-licensed software, or special approval required to use it), although unlike Google, they don't post their internal policy publicly.
If someone works at one of these companies, what do you want to do – spend your day trying to argue to get the AGPL ban changed, or a special exception for your project; or do you just go with the non-AGPL alternative and get on with coding?
The main reason it's a problem at many of the companies which ban it is they have a lot of engineers who readily patch and combine code from disparate sources and might not always apply the right discipline to keep AGPL things appropriately separate. Bright-line rules can be quite useful.
It is true that MongoDB's AGPL contagion and compliance burden, if you don't modify it, is less than many fear. It is also true that those corporate concerns are valid. MongoDB does sell commercial licenses so that such companies can handle their unavoidable MongoDB needs, but they would tend to minimize that usage.
