I've lost half a street of front only's to a trad cleaner doing the backs as well. (Too much hassle to do the backs wfp which I explained to the custies who were happy to accept F/O until someone came along who is prepared to do the backs as well.
However, I've picked up some nice big plush houses that some other wfp er was doing cause he does a crap job and I'm charging them more than he was.
All's fair in this game, you lose some, you win some.