While 301works might not be just a bit.ly stunt, it certainly was disproportionately important to bitly not to have a glaring example of the negative effects of URL shorteners staring people in the face -- they encourage link rot and offer the potential for lots of it. The potential for shorteners to disappear and break lots of links is certainly a massive flaw in their business model.
This whole link rot is massively over stated. Most short urls are used on Twitter. Who is reading old Tweets on Twitter? Almost nobody since Twitter is about now, not yesterday.
By the time you switch over to some 301works archive the links will have lost 99% of their relevancy.
I used to agree with you, but I think that both people and companies have an interest in preserving the conversation. Not every, or even most, conversations, but certainly some.
In which case you should be using your own shortener if you want to preserve your own links. Or if you're a company scanning other links then you should be resolving the short urls as you receive the entries.
