No big deal? Consider the fact that most of C++'s standard smart pointers still don't support atomic writes. Not Boost's (documentation), not Loki's (despite an MT ownership policy) not Scott Meyers's. What's that mean?
shared_ptrp(new int(42)); // thread A (supposedly owning) p = shared_ptr (new int(1942)); // re-writes p // thread B (supposedly reading) { shared_ptr p2(p); }
What otherwise looks like one thread owning the resource and another thread inspecting it, is actually undefined behavior.
Herb Sutter and Andrei Alexandrescu have written complex multi-part articles in the C/C++ User's Journal addressing variants of the issue, and almost always with corrections the next month. It's a topic almost impossible to get right.
The current state of the art seems to be led by Joe Seigh with his atomic_ptr. Apparently similar to patent 20060037026.
An "introductory" article can be found in the December 2004 issue of the CUJ, Atomic Reference Counting Pointers by William K. Reinholz.