SCM with locks vs. concurrent merges and team size

Question

What is the ideal number of programmers for lock based SCM not to become a severe issue in development?

Edit:

Fundamentally, I am not asking if there are merits to locking or merging (that is an unresolvable flame war). I am asking for the number of programmers where locking becomes a serious problem. I myself have found 4 to a good number, but this assumes the following

• most everybody works in the same office within yelling distance
• work is mostly disjoint (which makes locking not an issue except for common files {side note: my experiences is that merging is the best when there are little to no common files to accomplish tasks, which could be a series of questions on how does one organize code to such that common files are not needed by more than one person).
• the build can't be broken by premature lock release/commit.

Answer 1

Locks are an outdated concept. Even for a single developer - create a lock on your laptop, go attempt to work on another PC, and oops, you've got to manually intervene. With merge style SCM, you don't even have to think about it.

Answer 2

The ideal number of programmers when using exclusive lock is 1. Above, it's just painful, annoying, frustrating, etc. So, unless you're a team of BAs working on things that can't be merged (like word documents), don't do it, be real men/programmers and merge!