1 ...an angry young loser of a man who lived with his mother.
At the risk of sounding flippant, I'll point out that that one phrase neatly describes most of the members of the now-moribund Occupy movement.

On a more serious note, the parallels between then and now frighten me.  If anything, things are worse now.  Now, we have more nations bumbling around the world stage, acting just as foolishly and with just as much belligerency, and armed with weapons that make even the deadliest weapons of WWI look like toys.  Also consider the various Islamist terror groups, who are playing a similar role to the Black Hands, except that (a) they have proven themselves to be more motivated, better organized, and much more brutal, and (b) they have (or have improvised) weapons that are far more devastating than the crude bombs and pocket pistols the Serbian radicals had, and may yet gain access to weapons that are even more destructive.  (As a small aside, also consider that many Western nations, the United States included, have bred their own potential Black Hands; the above-mentioned Occupy movement, The Traitor Formerly Known As Bradley Manning, and recent British and Australian volunteers for international jihad are the bellwethers of this.)

2

There are ways in which things are far better now. For one thing, we don't have the row-of-dominoes alliances set up which led to a diplomatic cascading failure.

3 This is the first I've heard of the Archduke's policies. It sounds like if he had survived, things would be even better than we imagine things would be simply if the war hadn't happened.

4 Nuclear weapons really did change everything. In World War 1, the main fear of countries was that they would delay mobilization, their enemies would mobilize, and they would lose the war before they could properly form up their levies; this is essentially what happened in the latter wars of the 1800s, where Prussia won several decisive encounters through superior organization. Alsace-Lorraine was obtained that way in the first place, right?

Nowadays, the need to have your civilians drafted and mobilized is next to nil, and the rewards to be run through a devastating first strike are quite a bit smaller. No civilian militia or freshly-drafted troops could stand against a professional Western army (and, to be blunt, none of the other professional Western armies dare stand against the US; even the Brits and the French would be little but speed bumps). On the other hand, having experienced WW1, the Western countries are very hesitant to be the first one to pull the trigger. Even Hitler didn't resort to invading countries outright, without a buildup of public opinion and well-crafted justifications. (Of course Pete would probably say "I can think of one example!" ;p)

The biggest issue regarding world peace is that there was previously a system where the powerful Western countries demanded that the leadership of other countries take responsibility for the actions of their countrymen, and happily decapitated those who did not; the idea that a country would be considered "sovereign" but not fully under control of all its territory was silly. Now we've got a series of countries who can claim sovereignty within their borders without actually having control of the population within those borders; the penalty for toleration of such shamelessness has not been fully paid.

That said, the REALLY scary parallel isn't with the start of WW1, but the US's chosen tactics in WW2. We have previously denounced entire areas of warfare, such as the bombardment of cities or the use of unrestricted submarine warfare, as barbaric and completely incompatible with the behavior of a modern society; yet, when pressed, we embraced those strategies thoroughly and to the massive detriment of our foes. Should the new asymmetrical strategy of the employment of non-governmental combatants prove to be a true threat to the US, we would likely embrace that strategy as well. And how well would we do, with our acceptance of military necessity, our widespread gun culture and gun ownership, our legions of youth trained from a young age in advanced squad tactics, and our vast wealth coupled with our technology advantages?

(Basically, were it not illegal, could I see the same folks who play Counterstrike or League every night piloting remote killing-drones through the streets of Medina for the glory and lols? Oh yes, oh yes indeed.)