As Antechrist said, there ARE no "inside guys". The block chain works because in order to edit the chain to insert fake bitcoins, you'd need to edit every single block that comes after what you're editing. Imagine trying to add fake money to your bank account by creating a fake history for the money that dates back decades, including editing every single record of the money in every single account it was ever in and every single transaction it was ever in so it actually looks correct to anyone looking at the paper trail.....simultaneously. And every bank involved in the currency you're using has all of the complete records, so you need to modify it for all.
And said hacking gets harder as time goes on, because bitcoin works on a sort of "majority rules" system where it follows the longest block chain for determining verification. And as you add more computing power to a mining system, it increases the cryptography difficulty so it always remains at a consistent "One block processed every 10 minutes". So you're constantly needing more computing power because the editing you need your computer farm to do is increasing as you're in the middle of hacking it.
You guys keep saying it like this would be particularly hard. Simply put, it's not that secure, it's just not worth the outlay and time it'd take to blow it open. Largely because no electronic security is that secure unless you've pulled the network cord. Give it one guy who decides to turn his botnet against them, the power can easily dwarf any supercomputer out there and would be entirely capable of the needed operations. I'm sure they're very proud of what they have, I'm also rather sure that they're well aware that reaching any significant level of public interest would probably spell disaster for them in any number of ways that the currency could be faked, subverted or simply killed off.
Electronic security isn't about perfection, it's about making it take long enough no one's willing to waste their time to break it. There is a hole, and if someone else finds it first you're hosed. If you're using a bunch of hacked together contraptions you've got enough holes for an army to march through if needed. I'm saying this as someone who's spent months removing holes from various supposedly secure structures.
Just be thankful most of the bot net idiots point their efforts at spamming people.