I agree that that I can filter out noise on twitter by adjusting my followers. However, I had named twitter as one of the examples, I should’ve ventured into other networks as examples.

What about a real friend on facebook or linkedin who I would still like to keep as my connection but their constant messages, status changes and group postings on the network are almost spam like. I know on facebook, they have implemented filter ability based on what I would like to see on my timeline from certain individuals, but what about the rest of the networks?

This should be a normal ‘best’ practise on every network and future networks to come.

Maybe if twitter implemented a way for me to find a ‘real’ expert on the topic based on the tweets and not their profile bio?

Follow the people who give you quality.
If you’re not getting quality from someone, stop following them.
If you get noisy @messages from someone, block them.
Pay attention to RTs, because they’ll help you with #1 and #2.

If you are getting polluted with Internet marketing, then stop following, jsut as you would not consider their sources while in Connections. It is all about filering and yes, finding the true experts.. However, it isn’t what network you use most of the time, but how you use it. Some of the small niche social network sites have stronger experts than 300,000 that have profiles, blogs and bookmarks.