Sorry, my statement was more generic. I wasn't trying to say that Guido is motivated by money, just that these are common ways to get someone to stay if that is indeed the issue that makes them want to leave.
On the issue of challenges, maybe Guido has more pull on this, but there were recently some articles/discussion on HN about Google's hiring practices. They might hire you based on your PhD in databases, and then have you writing shell scripts for work because some randomized 'sorting hat' tells you what group you end up in. It's possible that even Guido doesn't have enough pull at Google to overcome this. :-\
If you want to move to another team at Google, it's really up to that team if they want you. As long as they have budget for you, and they want you working with them, then you're free to move.
The problem with new hires is that no other team has any idea whether you're any good, so it take a bit of tenure to prove yourself and make yourself known to others.
I'm quite sure Guido would be doing whatever he wanted at Google
The discussion I'm referring to represented ending up somewhere that you don't want to be as a bit of a trap.
E.g. if Guido ends up writing shell scripts, but his real skill-set/passion is for databases. It's quite possible for him to under-perform, and then that performance used as a reason for the 'database team' to not take him.
On the issue of challenges, maybe Guido has more pull on this, but there were recently some articles/discussion on HN about Google's hiring practices. They might hire you based on your PhD in databases, and then have you writing shell scripts for work because some randomized 'sorting hat' tells you what group you end up in. It's possible that even Guido doesn't have enough pull at Google to overcome this. :-\