A recent SM implementation with a national staffing firm confirmed virtually everything you wrote.
From a design perspective, I adopted the hybrid avatar to incorporate the individual’s face with the company logo. I’ve found that using a black and white head shot and overlaying it with the company logo in color is an effective way for the company’s color to pop out and creates a distinctive visual cue that is recognizable in the stream of tweets blowing by on the user’s monitor.
We insisted on a corporate twitter ID for each staff member instead of using their personal twitter ID’s for precisely the reason you described: we want to maintain ownership of the relationships built with clients and prospects in the event that an employee leaves the firm. They may leave, but the Twitter account and all of its followers stays with the company. We made the investment in building their network and we recognize the enormous value in 500, 1000 or 5000 devoted Twitter followers.
Although we did create a corporate twitter ID, we find that it is not really used an an interactive ID, but as a way for individuals to find us and direct future communications through one of our employees. The corporate Twitter ID is constantly monitored, but there is virtually no interactive traffic and its tweets are generally PR related – announcements of office openings, new hires, new company blog, etc.
Once the structure has been designed and implemented, it’s as crucial to have someone monitor all the corporate twitter streams. I’ve discovered employees who have tweeted inappropriate comments, revealed too much personal information and have used language that would never be allowed in any printed communications from the company. Every tweet reflects positively or negatively on the company and needs to be monitored for brand and message consistency. I wish it could be done automatically, but they actually have to be read and corrective action taken before any damage is done to the company.
Again, yes, there are many ways to skin a cat, but some tend to be better than others.