Such institutions, when guided by active participants who intensely feel the need to save such resources, can allow projects to outlive individual personalities and the limits of personal resources, a collaboration that fulfills an important aspect of their mission. I've had the opportunity to see some of the research initiatives in this area shaping up. Mellon Foundation, Cornell University, the University of Virginia, and a consortium of libraries, museums, and archival organizations with professional commitments to this question are working on the technical issues. There are many more technical obstacles than folks realize, and one of the biggest myths of electronic technology is that it is a good storage medium. Not in its present form.
Data are vulnerable, mutable, unstable, and unlikely to last.
A book is a much better bet, if what you're after is accessibility to an unpredictably distant posterity. This will change, but the issues are complex. Lastly, the artists themselves are going to have think through issues of archiving. The period from 1995 to the present marked an incredible proliferation of new media work on the Web, most of it completed and 'published' without traditional funding. In other words, as access to the multiple resources made possible by computers expands, digital media may not remain a niche predominantly defined by its medium.