My first foray into the temporary agency market was registering for Todays Temporary.
Trouble began when they experienced an accounting error during the summer. Somehow they paid me 50% more one week by mistake.  It was not noticed by me, as that week, I was on a one week assignment with a company.  Sonce it really wasn't much more than all my previous checks, I had assumed that my pay rate had just been bumped up.
I was in for a big surprise come holiday time.  They were justifying their books at the end of the year, and noticed the error.  Instead of writing it off as a loss, or bringing me into their office and breaking the news to me, they gave me even a bigger surprise.  It was the week before Christmas.  I would probably not be getting any assignments until mid January for the holiday slow down.  I went to pick up my check, and when I tore off the little perforated ends, I discovered that the secretary at the agency who merrily wished me a blessed Christmas had handed me a check for ZERO DOLLARS!!!
Apparently, they decided to deduct the error from my paycheck pronto.  A more rational thing, in my mind would be to slowly garnish my check for a few months, or, as mentioned before, just inform me.   
What a rotten lump of cole that was.
In fact, when I called up for an explanation, they told me they had another assignment for me, covering for a receptionist the day after Christmas.  However, I still owed the company $60.00, so I would be working for free that day.  
Of course, my reaction was to send my resume out to other agencies.   Too bad I wasn't hired for the data company that handled that agencies paychecks..