I just lost everything I was writing because Slashdot discarded my post when changing to plain text. I'm not going to hunt down references again. Google yourself.

Here's the rundown:

[I'm talking about the difficult in embedding Python in an application (extending the application. This is the usual domain of a scripting language.]

1) Python is huge. It is improper for small devices like FPGAs. Python weighs in at multiple megabytes.
2) Python is very difficult to sandbox.
3) It is difficult to have multiple independent Python instances running concurrently (GIL).
4) It is difficult to have multiple contexts. Python lacks proper coroutines.
5) Python is built with the extend rather than embed mindset e.g. [1].
6) Python is whitespace sensitive. It is unnecessarily difficult to write small embedded scripts or macros for your application (see WoW).
7) Python libraries make it difficult to embed in e.g. an ANSI C only environment.

[1] http://www.twistedmatrix.com/users/glyph/rant/extendit.html