I don't understand
For example, look at the Foscam line of cameras. Their most popular [indoor] model has pan/tilt, night vision, and is even capable of two-way audio (in/out ports, no mic or speaker), and it only costs $79 on Amazon. That means that for the price of two Dropcams, you could buy 5 Foscam cameras with more capabilities.
I'll admit, though, that the Foscam system has its drawbacks. You are responsible for a lot more stuff, like having a computer running at all times to record the data, and making sure that data is backed up to the cloud. Plus, you have to do a lot more setup, like installing the Blue Iris software (which is another $48). It's true. But you do get more flexibility. Foscam sells outdoor cameras, which I don't think is possible with the Dropcams.
Lets compare the cost of operating 4 Dropcam Pros to the cost of 4 Foscam cameras:
Dropcam Pro: $800 for cameras, plus $750/year
Foscam: $320 for cameras, plus $60-150/year for a Crashplan membership (which can back up all your other stuff too)
Both solutions offer remote access, but only the Foscam offers the ability to store unlimited amounts of video, and the operating cost doesn't increase when you add more cameras.
In the end, while I appreciate the polish and simplicity of the Dropcam solution, I just can't get past the price. This isn't like Sonos, where you pay a lot but you get something that just can't be replicated with less expensive alternatives. You really can "roll your own" and get a great system for a fraction of the price. Dropcam has its advantages, but I don't think they outweigh the advantages of the alternatives...
That said, there is a sense of satisfaction in rolling your own setup and it's something I'd like to do more research on. The fact that you can have outdoor cameras is pretty nice (you're correct that Dropcam doesn't have a suitable outdoor cam at the moment).
One side note: With Dropcam, if you're willing to only have 7-days of continuous cloud storage, you can get a subscription for all 4 cameras for a total of $250 / year vs. $750 / year. Still, that's pretty pricey.
Believe me, I'm not usually the kind of tech snob who insists that everyone should roll their own. In this case, though, I just can't get past the price of the subscription.
Yes, you can go with the 7 day solution, but that really wouldn't work for me. It's just not enough time. My wife and I just went out of town for 16 days, and if anyone had broken in in the first week, we wouldn't have that video anymore.
It's true that security is a concern. I'm not sure if there are ways to shore that up. I'll have to look into/think about that.