The truth is that we can't really identify the reason for the recent rise in fiat valuation of Bitcoin beyond saying that there is increased buying activity. Causal attributions to real world events are impossible, because all date we have are purely correlative.
In my opinion the upcoming release of Bitcoin 13.1 featuring Segregated Witness qualifies equally well to be a reason for price appreciation. In the long term, Bitcoin will simply increase in value compared to fiat because fiat money unlike Bitcoin is subject to inflationary devaluation. So Bitcoin is an attractive hedge against inflation.
ya.ya.yo!
In my view, the recent price rise from around $610-620 that had been there for over two months up to today's $690 should rather be attributed to the effects of this summer reward halving that finally hit the market and tell on the Bitcoin price in full. If this is really so, and I hope it is, we may see a further rise in price as the Bitcoin supply is diminishing, and consequently being overwhelmed by the demand.