Update: In July 2012, Twitter cut the link with LinkedIn. No longer can a user of both Twitter and LinkedIn have their Tweets - whether selective or all - automatically show on their LinkedIn home page. (We'll address an easy "work-around" in an upcoming blog post, however.)
A current discussion in the LinkedIn group "On Startups - The Community For Entrepreneurs" is addressing how to use LinkedIn use for entrepreneurial businesses. One recommendation is to tie your Twitter feed to LinkedIn so your tweets appear on your LinkedIn profile.
Being an entrepeneur and consultant, I have done this. Here's how my most recent tweet looks on my profile page:

However, a group member commented that she would never put her Twitter steam on her LinkedIn profile because she "would never combine a cocktail party with a job interview."
For me that's not an issue, because I only use Twitter for professional purposes, to provide or share content and thinking on strategic planning, marketing and other business topics where I can add to the conversation, learn from others similarly engaged, and even offer a little thought leadership.
Yet, even if I did mix my professional tweets with "cocktail party conversation" tweets on Twitter, I could separate the conversations so that only my professional tweets show on my LinkedIn page.
The secret? Use Twitter's hashtag feature.
First, here's how to add your Twitter feed to your LinkedIn profile page. Go to "Profile" and click “Edit My Profile.” Then click “Add Twitter account” next to the Twitter label toward the bottom of the box that summarizes your employment, education, connections and websites.

Twitter will ask you to verify your account name and password. Then you’ll be asked by LinkedIn how you want to share your tweets on LinkedIn. Check the "Display your Twitter Account" box:

You will see a check box that will limit what you share to only those tweets that contain #in or #li. Check it!

Voila! That's the magic. Now anytime you tweet something that you'd like to appear on your LinkedIn profile, just be sure to include the hashtag #in or #li in the tweet.

If you don't want a tweet to appear on your LinkedIn profile, don't include either of the LinkedIn hastags, #in or #li.

You can always change your Twitter display settings on LinkedIn. Hover over your name at the upper right side of your LinkedIn screen.

You will see "settings" in the menu - click on it. After you sign in, you' ll see under the "SETTINGS" heading "Manage your Twitter settings."

Click on that for options.

When you have the "Share only tweets that contain #in (#li also works) in your LinkedIn status" clicked on, that's all that will appear to those people who you want to view you on LinkedIn as professional, business person, not as an over-served cocktail party guest!