Twitter replaces an awful lot. It replaces live sport, breaking news, your actual friends. It's great for connecting you to people and events and it's true to say that almost everything in which I have an interest (museums, galleries, sports teams, newspapers, travel destinations) has an associated Twitter feed, in many cases a better start-point for information than the website. I always try to explain Twitter to people as an information-filter: it's about the information that you gather in, not the information that emanates from you. Twitter is for your eyes, not your mouth. My own use of Twitter has changed over the 5+ years I've been a user (phrase deliberate). I now use it in a far more professional context, which may explain why I've become more dull over time.
A recent study shows that over 70% of Twitter users check their feed within 3 minutes of waking up. Leaving aside this most obvious way that Twitter can ruin your life (addiction), there are several more subtle negative aspects to Twitter. Guard against them.
1. Only following people whose opinions you agree with.
Being open to ideas and opinions is important, but following only people who agree with you is likely to cement your position even before a discussion has started. I've had the misfortune to work with one or two people whose confidence in their right-ness was astounding. If at any point you disagreed with them, you were either an idiot, or someone who had simply not thought enough about the argument: think it through again, and I'm sure you'll agree with me. If you are going to argue, it's important to be open to persuasion. It's the discussion that should be important, not the 'winning'. It's also hard to 'win' an argument in 140 characters, especially against someone with a long-ish Twitter handle. For every person who agrees with you fundamentally, try to follow one who doesn't, unless the first person you followed was the Anne Frank house, for example. You'll find your feed has far more balance and you might even come to respect the opinions of those who disagree with you.
2. The over-thought Bio.
Changing your profile picture on a regular basis is just about acceptable, but changing your Bio is odd. You are not David Bowie and you don't need to continually re-invent yourself. I'm not even sure what the point of a Bio is, and if you're trying to crow-bar some comedy into what you write, stop it. Stop it now. There are some things that shouldn't need to be written: if you have kids, we take it as read that you think they are 'wonderful'. If you work in IT, you do not need to state that you have 2.0 kids (that joke became obsolete around the same time as the ZX Spectrum). Stating that you are 'partial to the odd glass of wine' does not make you sound like a lot of fun, just someone without any genuine interests. The Bio is meant for people to see at a glance if they wish to follow you or not, but reading the top 5/10 Tweets from someone's timeline is a far more reliable way of telling what you're getting. It didn't take me long to find two examples of bafflingly pointless Bios:
'Editor and professional procrastinator. Massively confused by the whole thing'
'Curmudgeon. Neither in School, nor of school, but by school. Brace yourself - there may be a kerfuffle'
No, I've no idea either.
3. Your dinner.
No-one cared what you ate for dinner before you were on Twitter, and nothing has changed. Did you ever take a polaroid photo of your evening meal and pass it round the office the following day? (note: this is rhetorical, I hope). By all means post photos of your culinary creations, but to avoid a false sense of over-importance, you must first assume that no-one is going to view them.
4. Being proud to be blocked.
Blocking people is fairly unusual. The only people I ever block are generally spam sex-bots with alluring names like @ej35xxx80. Famous people with lots of followers seem to have endless reserves of patience and will generally threaten blocking before actually doing so; you've actually got to be pretty offensive to have people hit the block button on you. Being blocked shouldn't be something to be proud of, but I've seen lots of Bios where people are delighted to state that they've been blocked by someone they disagree with, which strikes me as wrong.
5. Protecting your account.
Twitter is public. It's pretty much the whole point of Twitter. If you want to protect yourself from everyone but your nearest and dearest, that's what Facebook is for, your real friends. People with 7 followers and a protected account might just be missing the point. I'd understand if what you're writing is top secret (maybe you're working towards who really killed Kennedy), but then Twitter is probably not your ideal medium.
And now I'm off to make some truffled eggs. Photo on Instagram in 5.