I don't own my own company and I certainly don't get to pick my own clients. Even people that pick their clientele don't always 100% stand behind them (possibly they accepted them as a client for financial reasons, or favors.). In an ideal world though, your PR rep truly believes in you.
That said, when a publicist shouts out a client in a non pitching manner, say on their blog or twitter or even in conversation, I do not think it is a business move (at least not directly). I think they actually believe in what they are promoting. Naturally we are skeptical to think that they are being biased, but a publicists grass roots are in word of mouth. When I trace back to the root of why I became a publicist, it only made sense. Whenever I found a food or a band or something else I loved, the first thing I would do is pass that information along. It was a natural promotion. When I found out that this actually had a name and it was called public relations, I knew what I was going to make a living doing.
People shouldn't be so skeptical about publicists promoting clients on their own personal time (I'm not talking about a company format). If they didn't support them on a personal level, they would not bother supporting them on their own time. They would leave it to the business hours, and not take the extra step to shout them out.