I find myself wondering if you actually read the content. Your first paragraph seems like a response to the article, but then your second makes it look like you didn't. Are you encrypting your files via hand-calculations before putting it on Dropbox, or using a second software package you installed as a tool? In which case what exactly is so hard about using one of the transparent file systems, which both boast a decent array of OS support options, that you have some sort of solution for that doesn't involve installing something beyond Dropbox?

I'm not sure if we both read the same comment. The second paragraph focuses on the fact that Dropbox is not suitable for sensitive content, and therefor he suggests using another service that offers client-side encryption (Tarsnap, possibly, as I think that it does that). He is not saying that he is putting encrypted files on Dropbox.

exactly, for sensitive data I use a different service that does client-side encryption: CrashPlan

More on their encryption options here:

http://www.crashplan.com/blog/tag/crashplan-encryption

You misunderstood my response. I use Dropbox for syncing of non-sensitive data across devices. For sensitive data, I use something else entirely: Crashplan with client-side encryption