UNIX pipes

why does this work: firefox yotsuba.jpg
but not this: ls|grep yotsuba|firefox

note: ls|grep yotsuba produces: yotsuba.jpg

what am I doing wrong?

You're the idiot.  Everything is a binary.
Can I quote that? Like...all the time?

"XML is nice, cause you can edit it with a text editor"
``No you can't! It's a binary. Everything is a binary''