Want to send some secret text to someone else?

[GreyGeek]

Email them a picture or music file, or post to FB or some other social website.

[Don B. Cilly]

If FB or the mail provider are running stegdetect (and if the provider is Google... they probably are :·) you'll end up on a lot of lists you'd probably not want to end up on...

[GreyGeek]

The available version of stegdetec hasn't been maintained for three years and is considered abandon. Also, it only detects hidden texts in jpeg files. To decode png or bmp images you'd need zsteg. Or stegsolve.
As far as Google and the others go, they probably already have a complete mapping of my storage device and have probably snooped into a few files.
Text buried in an image can be a transform of an encrypted msg which yields garbage when zsteg, or what ever, is used.

Then there are less obvious methods which involve shifting the LSB of pixels in a hires image by one bit. The transformation is not visually detectible and stenographic detection would reveal nothing. The resulting 0's and 1's form the binary message. Every 25,600 pixels would store a page of ASCII text. A 1Mb png could contain about 5 pages of text.