Sure but these things cost money and we have finite resources. A dedicated fMRI machine would cost somewhere between 2-6 times SIAI's annual expenditures.
That's a separate argument than the one over whether such a scan is possible with present technology. I do agree that an fMRI machine shouldn't be a budget priority for SI; I also do not consider it worth my money to get frequent MRIs (although I have saved the one I got for other reasons last year). If I were sufficiently wealthy, though, I'd buy frequent brain scans before I'd buy, say, a Ferrari (and I do really enjoy fast, flashy cars).
Paul Christiano recently suggested that we can use neuroimaging to form a complete mathematical characterization of a human brain, which a sufficiently powerful superintelligence would be able to reconstruct into a working mind, and the neuroimaging part is already possible today, or close to being possible.
Paul was using this idea as part of an FAI design proposal, but I'm highlighting it here since it seems to have independent value as an alternative or supplement to cryonics. That is, instead of (or in addition to) trying to get your body to be frozen and then preserved in liquid nitrogen after you die, you periodically take neuroimaging scans of your brain and save them to multiple backup locations (1010 bits is only about 1 gigabyte), in the hope that a friendly AI or posthuman will eventually use the scans to reconstruct your mind.
Are there any neuroimaging experts around who can tell us how feasible this really is, and how much such a scan might cost, now or in the near future?
ETA: Given the presence of thermal noise and the fact that a set of neuroimaging data may contain redundant or irrelevant information, 1010 bits ought to be regarded as just a rough lower bound on how much data needs to be collected and stored. Thanks to commenters who pointed this out.