While I agree with the last two sentences, it's worth noting two points which undercut your first two sentences rather dramatically:
(1) Taking BSD-licensed code and making a proprietary fork doesn't make the previous release magically go away; it makes a new fork. If I love the open source editor FooEdit and FooEdit has a vibrant community around it, then somebody else comes along and starts selling BarEdit based on their proprietary, closed source fork, I can either choose to switch to BarEdit and accept the risks, or keep using FooEdit. (And arguably that's not a binary proposition in the first place: I can switch to BarEdit and then switch back to FooEdit.) The worst case hypothetical is that somehow BarEdit's creation kills the FooEdit community, but in reality that seems very unlikely; in practice, I can't think of a single BSD-licensed project that this has happened to. Can you? Yes, it's possible that in my scenario BarEdit would get cool new features denied to FooEdit users, but if you're deliberately choosing your software based on its "openness" then you've already decided to forgo cool features that are only in proprietary software. Furthermore, you can hardly point to BarEdit and say, "those cool BarEdit-only features would be in FooEdit if only it had been under the GPL"; the more likely case is that BarEdit would simply never have existed.
(2) While the anonymous coward who responded with "ROFL" was perhaps unduly acerbic, his point is correct: an end user who can't debug and patch code is dependent on the developers to fix bugs regardless of the license the software she's using is under. As much as people don't like to hear this around these parts, I know an awful lot of end users who look for free software because it's free as in beer.