Hidden encrypted messages

If true encryption is ever outlawed in the U.S., I wonder if it's possible to have an encryption technique that preserves plausible deniability. That is, if seemingly innocuous messages could contain encrypted messages (for example, first-letter-of-words strung together). In such a case, I'd think that it would be difficult to prove that said message contained a hidden message unless the decryption key was available (the embedded encrypted message wouldn't look suspicious, even if an onlooker knew where to look). Is this a common idea in cryptographic circles? derek