Twitter was the "founder" of this issue, even then, it is not really a problem. It is more of a house cleaning task that can be cumbersome depending on how much data you consume. Although; there are some statistic websites that use your followers to following ratio as a measurement. If you follow more people than follow you there is a high probability that you are not producing interesting original content and could be engaging in follower spam. Follower spam is when a user follows other users in the hopes that they will follow them back after they receive their new follow notification.
This is currently not an issue for Facebook because they have just launched their subscribe function. On Google+ it is also limited because Google, for now, (and Facebook) only have this feature available for a real person. An non-human account is more apt to walk away and stop updating a service than an actual person is. That is why this is much more prevalent on Twitter. There were many Twitter tools, like MyCleenr, at one time that would scan your account to find when each account's last status update was and unfollow inactive users automatically. More recently most of them have had issues staying open because of Twitter's more stringent API rules.
Google+ is interesting because it is so new it does not seem like this would something people are even thinking about yet. I actually was! Just last week I started to look through my Following Circle to see who had never posted in a way I could see. What happened in the early days of testing is that many G+ users followed interesting people, but the service was so new that not seeing a post was normal. Now that Google+ is at the ripe old age of 3 months, and public, it is time to settle in and manage who we have Circled.
Today I came across the Chrome extension Uncircle+. It makes use of Google's recently launched API to scan everyone in your Circles to determine who has never updated their status in a manner that you could see. You then are given a list of those users and have the option to let Uncircle+ automatically unfollow them or not. This is very useful to clean house, and can be very beneficial to people that are up against the 5,000 people in your Circles limit. I downloaded and used version 1.1 of Uncircle+ without an issue. Give it a try and let everyone know what you think in the comments below.
Clicked on Find Inactive People after launching the extension.
Everyone in my Circles was scanned and it found 40 people that have no posts. The "I" above mean Inactive and the "E" means Error (one of my Circles users had been banned). Because I was testing the extension I right clicked to open a new tab on every person that was said to be inactive to verify; the extension was accurate.
I unchecked users that I did not want to uncircle.
After clicking Remove Selected it shows who was removed. Again, I verified for testing purposes, they (and only they) were removed.