The idea of a secure network and a VPN to get into it if you're working away from the office is all very fine, but the list of problems it throws up is huge - and it just gets bigger as your company expands:
- You almost invariably wind up with a two-tier experience. People who are in the office and get nice fast access to everything and people who are out of the office and everything's dog slow. Oh, sure, you can reduce this problem somewhat by putting servers in a colo, but now you've got to engineer systems so you don't wind up with everyone getting the dog slow experience. (I'm particularly looking at legacy file servers here; SMB was never really designed for use over a slow, high-latency link, though I understand newer versions of Windows Server have mostly cracked this).
- You don't gain an enormous amount of security. Even with a heavily locked-down perimeter firewall it's seldom that difficult to figure out a way to get information out, as long as you can get something nefarious in. And that really isn't difficult with a little light social engineering.
- Expanding beyond one office gets very expensive very fast. You need to be looking into Terminal Server, very fast (=expensive) links or have branch offices put up with terrible application performance. IT as an industry automatically assumes that multiple branches = huge business with a huge budget that takes IT very seriously (seriously, throw that bit of information into any proprietary system you're pricing up and watch the price skyrocket). I can tell you now that every single town has loads of small businesses spread across multiple branches that don't have a huge budget, don't feel the need to dedicate enormous resources to IT and they are absolutely loving the various web-based products such as espoused by Google.
Oh, sure, there's a lot of business applications that are designed on the assumption that you're a company in just one office - or if you have several offices, you have gigabit links between them - but I don't think Google really need to care too much about those.