I keep coming back to this idea over and over. DabbleDB was sort of like this but it closed shop after a talent acquisition. Formstack.com (formerly hosted at formspring.com) had very cool table-building tools but it appears they pivoted to become yet another Wufoo/SurveyMonkey. JotForm is somewhere between Wufoo and a database. FormLogix is another form-builder. Hyperoffice.com and Zoho.com/creator sell themselves as MS Access alternatives. FileMaker.com is probably the closest thing to pg's request.

Nevertheless, I still feel there exists a sweet spot that nobody has managed to reach yet. But I don't know how I'd go about finding out if people would really pay for a good excel-db hybrid web-app or not, considering so many alternatives exist, many of them nearly free.

Along with DabbleDB, bList (also acquired, by Socrata) was the other startup mentioned at the time as satisfying this idea.

Also, FileMaker / Bento

I am working on such an app over Google App Engine, which also integrates well with other Google services..

iFreeTools Creator : http://creator.ifreetools.com

Sounds like: http://www.resolversystems.com/products/resolver-server/