One of the main strengths of Twitter is the access you have to so many people.
However, the obvious counterpoint to that is that they also have access to you! (Unless you protect your tweets.) I use Twitter in a business/social hybrid model, so I prefer to have an open feed.
Good quality retweets are the gold dust that makes Twitter glitter.
I've found you need to be selective in what you retweet, but also be fair and return the retweet favour where possible. Receiving genuinely interesting information from your followers is part of the pleasure of Twitter, as is sharing your information with them.
However there is a dark and unpleasant entity lurking in the shadows - the auto retweet bots. These beasts hide in the "cloud" and pounce upon unsuspecting tweets and take them over for their own ends.
Some retweet bots are relatively harmless, like the "knitting" or "coffee" ones. (Don't ask!)
The ones I really have a problem with are those that add their own link to your original tweet and make it look like you endorse them. How many people would bother to check the original content? For example: One of my tweets was hijacked to direct people to a video of someone performing a very bad cover of a rock classic.
I particularly dislike it when bots pick up on my fibromyalgia and then purport to offer a "cure". Peddling nonsense has always been an internet speciality and Twitter is an ideal platform to promulgate the genre!
I know that by choosing to engage on Twitter that I take have to take the rough with the smooth. However, that doesn't stop the intense irritation nor the righteous indignation flaring up on occasions.
All I can do is hit the block button and hope my Twitter glitter isn't too tarnished.