Blogs extend a company's a brand. This is especially true in the case of a professional services firm.
A professional services firm's brand is based on the expertise of their employee professionals. There is nothing to drink like Pepsi to make customers feel good or shoes to look cool in like in the case of Nike's brand.
Traditional marketing of professional services is based on extending the reach of this expertise - getting the firm's employees in front of existing customers, prospective customers, the media, the public and other sources of referral work. The concept is based on the sharing intellectual capital - the more you did, the more people exposed to this intellectual capital, the stronger the brand.
Extending the reach of your employee's expertise is done through writing, seminars and interviews. Problem is that once the seminar was over or article was old this sharing intellectual capital was gone.
Blogs share this intellectual capital - except it's like doing so on steroids - the intellectual capital is shared at the 'go to' place for information - the Internet. Content is preserved, indexed and optimized in the world's library - Google. Content is streamed by RSS so people get the news when they went and how they want it. Best of all it is dirt cheap - far more cost effective than a seminar or a lengthy article for professionals whose time is their stock in trade.
The key is making it easy to extend the intellectual capital or the brand to the net. God knows marketing people in firms are swamped - they do not need another 'great new idea' that takes a ton of time. So use the intellectual capital the company has already reduced to digital form - the content they've already produced.
Where's this existing content? Articles, interviews, email newsletters, Web site content that is not indexed or optimized and seminar materials. Book publsihers and authors have a ton of content (hint for you, Steve)
You'll be surprised to see all the stuff that's been written. Get it up on a blog on the net and get this content working for you and your clients.