The issue for me is never the archive — I take archiving seriously and do it early and often. Triple redundancy is my approach to e.g. the photo hoard.
The issue with both online and desktop image management apps is the hours of labour one puts in to organising, presenting, and tagging. The value I have sunk into Flickr (I have a Pro account due to my storage use) is not the photos themselves, all of which are stashed somewhere on my RAID backup device at home. It’s the time I spent organising them into Albums, tagging with comments and captions, etc. The “value added” that the tool allowed me to achieve, but did not allow me to migrate when the tool was abandoned by the vendor.
For photogs this has been a sad history. Google drops Picasa. Apple drops both iPhoto and Aperture. Many photogs, when their app of choice was withdrawn from market, faced a truly ugly (in some cases never successful) challenge to migrate their tagged and rated photo archives to other vendors’ tools. The nonexistence of an industry standard data interchange format for photo organising and tagging made this a nightmare.
The best protection from the inevitable rise and fall of tools and companies, of bad or good strategic decisions made by corporate honchos who are, truth be told, not that much smarter than the average bear — the only real protection — is open standards and interchange formats that enable us to port our invested labour to a new toolset. Who would use a text editor or spreadsheet that could store our work only in some proprietary format that no other tool in the world could read? Yet we are still using image management tools without any solid, standard data interchange format for this type of project, which leaves us uncomfortably exposed to corporate failures and changes of direction.