I went into partnership with someone last year, he mainly did design and CD-ROMS, and I did web programming. As a company we have various different clients, some who required one service, with others required another.
The problem we had is that at times one of us wasn't very busy, while the other was absolutely snowed under, working evening and weekends. At the end of the month, both would be paid the same amount, and any profit left in the business.
Our partnership ended, mainly because I went on honeymoon for two weeks and was still getting paid (we agreed we'd get paid for holidays). During these two weeks, he was left to handle every client, was absolutely bogged down with work, and got really annoyed that I was still getting paid while he was working his but off. Most of the time it had been the other way round, with my bringing the most money into the business, but I didn't complain. Anyway, my partner decided to move away from the business and take his clients with him, where he wouldn't have to share any of his profits.
Since then his main client who provides 99% of his work are in a bit of a financial pickle, and he's owed just over £20k for the last 4 months work, they just keep putting off paying him. So in a way I'm kind of please the partnership didn't work.