@MrClass: I'm in no position to give financial advice, I'll just share my interpretation of the events. I don't think Silk Road 2.0 has much to do with the recent spike, especially given the rumors of it being a honeypot for the feds. I suggest you read
this article for an in-depth analysis. Selling now means you are betting on this being another bubble. While it certainly looks and feels like one, things have changed since April. Many new VC investments have been made in the bitcoin space, and the involvement of the Chinese further solidifies bitcoin's legitimacy. I still personally think there will be a correction and the price will drop for a while, but that's just my personal opinion.
@rtp: indeed, 4100 BTC were stolen from an online wallet service. This is not a vulnerability in bitcoin itself, but in the wallet service. That being said, you shouldn't store your private keys in an online service that you do not control.
As for the "bitcoin vulnerability" paper linked in the MIT Technology Review article you shared, the paper has not been peer reviewed. Gavin Andresen of the Bitcoin Foundation responded:
However, it is good to note that in my initial review, I believe the paper’s assertion of a fundamental flaw is based on some over-simplified assumptions about how the bitcoin mining market works.
More:
Is Bitcoin Broken?