Ok, my shush account concept is causing a bit of confusion with some folks so here's some common answers.

1) a "shush" account is just a normal Twitter account. It doesn't tweet and serves solely as a topic placeholder. Why? See 2)

2) If you decide to tweet about (say) Blackberry mobile phones (and you don't think it is relevant to your regular followers) then you can prefix such tweets with the @shBBerry account (i.e. a Twitter reply)

3) Because of how Twitter replies work, only your followers who additionally follow @shBBerry will see these tweets.

4) Therefore you probably want to let people know that you are using sushes like @shBBerry. For instance you can tweet it occassionally ("hey, I'm also using @shBBerry", you can put it in your bio, you can put it in your Twitter background (look at mine), you could give them an auto reply when someone follows telling them about which sushes you use (this is the only time I've come up with a good reason to use such a tool!)

5) I've only created shushes which are relevant to me (listed here). Please feel free to create more. Best to prefix them with sh (for "shush!")

Hopefully that sheds a little more light!

updated:

6) Why don't shush accounts tweet? Because they are only acting as topic placeholders. If they additionally tweeted then, when you prefixed your tweets with (say) @shBBerry, are you tweeting about a topic or replying to a tweet from @shBBerry? Therefore, to avoid confusion shushes do not tweet.

Here is the current list of Twitter Shush Account which I've created:

@shBBerry

For Blackberry related stuff.

@sh4SQc

For Foursquare checkins (so you can prefix your shouts). There will be probably be a sh4SQ account for general 4SQ stuff real soon - I need it.

@shEbayL

For Ebay Listings (not Ebay general chat)

@wcTalk

For WorldCup tweets (note this is an older account so it wasn't prefixed "sh")

@chatonly

Misc chat but perfect for when you tweet from live events.

If this list reaches a certain point I'll have to create a separate site and have a proper, searchable database of shushes. However, that's a nice problem to have and let's cross that bridge when we come to it :)

I've also created a Twitter list of all these shush accounts.

If you've created an account then please let me know what it is and I'll add it (please try to start all shushes with an "sh" and remember that such accounts should not tweet).

@sh4SQc ("ssssh Foursquare checkins") is a Twitter Shush Account designed to help minimise the noise created by Foursquare checkins.

If you are a Foursquare user and have set up your Foursquare account to broadcast to Twitter when you checkin then you CAN prefix such checkin shouts with @sh4SQc to help hide such updates from your regular followers (who might not be interested).

If such followers have decided they DO want to hear about Foursquare checkins, then they can always follow the sh4SQc account to tune in to such broadcasts.

...easy as that :)

Obviously it's important that folks know about these shush accounts - one way it to highlight on your Twitter background or your bio which shush accounts you actively use.