With 150K unique visitors a month, they'll be lucky to get back a 10th of that - in bankruptcy court. What I'd like to know is how this unfolds typically with VCs when they anticipate that they will not get their money back. Can they shut everything down right away and demand all remaining funds be returned on the spot or do they typically assume the loss, write it off on their books and let the company burn through its remaining cash and grind to a halt naturally? I'm assuming the latter.

Firstly, I think they are getting a lot more than 150k visitors a month. The Alexa numbers suggest more like 10x that.

That is not a lot of visitors. My one man static content site is getting about 200k (high value niche) visitors a month.

A search engine is likely to depend on ad revenues. It might be able to target its ads better and to get high click through rates, but also needs to serve a lot of low value searches so I cannot see how it can make enough to justify a valuation that is anywhere close to a positive return.