I have to admit that the "difficult to build applications upon" is not the best selling point to put up there. But I stand by the security being difficult to q

I have to admit that the "difficult to build applications upon" is not the best selling point to put up there. But I stand by the security being difficult to quantify in Bitcoin because the mining reward (plus fees) is necessarily small in comparison to the transactions that are being moved (e.g. 25 bitcoins today vs potentially millions of bitcoins moved per block). The problem is that with a bit of coordination from the miners, forking is easy and easily profitable.