<p>At what point in a team's growth must process change drastically?  A lone coder can get away with source control and a brain. A team trying to ship large prepackaged software to local and international markets must have a bit more in place. </p>

<p>If you've experienced a large transition in 'process':  Was the team's process successfully changed with the current members or was the team itself mostly replaced by the time the process change came?  What were the important aspects that changed, were some unnecessary?</p>

If memory serves me correctly anything above five people is where things get dicey.  The number of paths of comunication between the team gets really large after that.
(2 people = 1 path, 3 = 3 paths, 4 = 6 paths, 5 = 10 paths and so on).
The last three places I've been the IT team went through a massive process change.  Yes, you will lose people, probably some of the better ones too.  it's not that they are stubborn and trying to stick to the old ways, it's just that a change like this will cause a mass amount of stress.  There are deadlines to hit and a need for quality to be met.  People will get confused about what process they are supposed to do, and many will fall back to the "old ways." (i've  been guilty of this too I admit.)
The key to succeeding is to take it slow and in small steps.  People need to take time to understand why the process is changing and how it benefits them.  That is huge, if you don't take time to do this, it won't succeed, and key people will end up quitting causing turmoil.
One of the things to absolutely remember is that ultimately some turnover is good.  It brings new ideas and people with different (and sometimes better) skill sets.  You shouldn't try and force change onto people rapidly, but they shouldn't be a barrier either.  If they don't agree with what is going on, they should either try and come to a middle ground with the people making the process or leave.  One of the real eye openers I learned at my first job is that in reality everyone is replaceable.  Someone will eventually be able to step in take the reigns.