When you land a VC deal and get $4mil, are you going to dance around with euphoria and say "we did it! we did it!" or are you going to say "well, that'll be 2 years to capture x percent of the market instead of 7 years- I hope it was worth giving up x percent of the company." If only the former, then you can take that as a clue right now that your business isn't quite ready probably.
(I'm being a little facetious- of course you'll celebrate regardless).
At too many startup conferences I've been to, the message (explicit or implied) was "you need VC funding".
I'm sure it's not always true.
Microsoft is the best example of this. I think ViaWeb may have done something similar before its acquisition.