I still think in the long run that its far more practical to develop a working prototype, find some investors, and then release under a standard commercial license model. To improve chances of reaching critical mass, the product should allow full use of the functionality - but shut itself off (or require reactivation) after a given period of time.* Much like Microsoft did with the beta edition of Windows 7. That allows the end-users to see what you've come up with, help identify bugs, and suggest improvements.
It further allows the developer to:
- get valuable feedback
- accurately determine the level of interest in their product
- build a database of users for future marketing and PR efforts
Note that none of the above requires the use of "open" anything - be it source code or the licensing model.
Open, as a
monetization strategy, only really works for major software projects (Apache, the kernal, etc.) where there's either an ongoing market for
corporate customer support - or where enough people are making money off it (e.g. hardware appliances) that the manufacturers view contributing code and money as an act of "enlightened self-interest." (Big corps like Cisco, Microsoft, IBM, Google,
et al do that all the time.)
For smaller projects, asking for contributions seldom brings in more than a pittance regardless of the number of actual users.
Maybe I'm overly cynical about these things, but to me crowd-sourcing software development sounds (in most cases) very close to this:

I think a lot of it is born out of the attempt to make some money without actually having to sell somebody something. It's a nice idea. But if the primary motivation is to get away from having to market or do selling, you can forget it.
Yes, there are a few Cinderella stories out there about how something became an epic success without any traditional marketing. But for every one of them
there are tens of thousands of other successes that came about through intelligent marketing and sales efforts. Truth is, if you want better odds of success, try copying what has already been proven to work. And only if it fails try something different.
So rather than go through the hassles of coming up with yet another alternate development model (since we have freeware, shareware, adware, open, and commercial models already) why not try going with a standard "closed commercial' license approach and see where it leads? You might be pleasantly surprised.
It's certainly easier to attract investors doing it that way if nothing else.
Just my 2¢
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*Note regarding deactivation of beta or trail versions:
I would humbly suggest that if software does deactivate after its authorization expires, the developer still allow the user access to any user entered data stored in the program after the expiration. Some export to a standard file format (tab delimited, CSV etc.) would be nice. Remaining functional in a read-only mode would be even better. That way, the user still has access to
their data, but is not allowed to modify existing entries or make new ones. I think that's more than fair because it strikes a good balance between not taking anything away from the user that belongs to
them while still protecting the developer's interests.