Police information gathering tactics have long-term consequences. Activists have been consistently stopped and searched while attending demonstrations in recent years. Some know their rights and refuse to give their details, which can result in the trumped-up temporary arrests mentioned in the previous post.
The more well-informed protestors become about police tactics, the more careful they are inclined to be. People attending protests these days may well decide to leave their ID, bank cards, and any other identifying materials at home so that a police search will not necessarily result in their identity being revealed. (Of course, such searches are often abuses of power, and technically police do not need to examine your ID during a stop-and-search, nor do they have the right to do so - but it's a common abuse of power, and people have become understandably cautious.)
This caution not only risks provoking an escalation in police tactics, it has immediate consequences to the activist. Travelling without any ID limits your freedom in the UK. Without bank cards, you cannot access cash; whatever money you may need while demonstrating, you have to carry on your person, making you more vulnerable to theft. For extended protests like the Climate Camp, this can indirectly result in seriously limiting protestors' movements. Travel is an issue; Oyster cards are almost always connected to personal details (even if yours isn't registered, if you've ever topped it up with a bank card then it can be connected to you), and public transport is more expensive without one. Cars are always linked to someone's personal details, and you are obliged to give your personal details if you are stopped while driving one - regardless of the reason given for stopping you.
Anonymity is increasingly difficult to maintain in the UK. We are tracked and recorded everywhere we go, and the police have access to national databases. The basic precautions necessary to try and slip through the net of police information-gathering require a level of personal inconvenience which many would find off-putting. (And yet the alternative is being entered into the FIT/NECTU/etc system of harassment; I can see how facing a choice between the two would put people off attending demos at all.)
After being badly mistreated in the past, many activists are disinclined to trust gestures of good faith from the police. The caution resulting from systemic police misconduct can continue long after that misconduct has stopped.
This also has PR consequences. Some protestors choose to wear bandanas or balaclavas over their faces to avoid being identified by FIT. This has the effect of making them appear dangerous, and as if they have "something to hide". To the general public, it makes the protestors look like thugs or criminals, which aids the police and tabloid press in their negative spin.
A similar issue results from self-defence efforts by protestors. For instance, the Blackheath Climate Camp was cordoned off by metal fencing before the tents were pitched. This wasn't intended to keep the police out entirely, but to secure the camp against the sort of baton-and-shield 'clearance' perpetrated against previous sites. Pre-emptive self-defence measures like this seem perfectly sensible in context, but to an outsider they can give a hostile impression. Before the decoration went up, the fence gave the camp an industrial, unwelcoming feel - and the opening day of the camp was a key photo-op for the media, as fewer members of the press came back to take photos of the decorated fence in later days. To someone who didn't know how police behaved at previous camps, the fence gave the impression that the campers wanted to keep people out, when in fact the camp was open to the public; one of Climate Camp's stated objectives was to educate the public about climate change issues. The unapproachable atmosphere which was unwittingly created by their self-defence measures was not only useful to police propaganda, it directly hindered the outreach and educational aspects of their campaign.
This broad issue was raised at the meeting of the Civil Liberties Panel, when Pat Reynolds, who was caught in the Climate Camp kettle at Bishopsgate, asked what the MPA considered an acceptable level of self-defence against police violence - a question which unsurprisingly went unanswered. The police have established a system where protestors are damned if they do, damned if they don't. If they defend themselves against a baton charge they risk being cast as "violent", which justifies further violence against protestors. If they don't they are hurt more badly (and as recent stories have shown, they have no real chance of making a successful complaint). If they do not attend a protest anonymously, they will be entered on a police database with all the unpleasant consequences that entails. If they do, they suffer personal inconvenience that limits their freedom of moment, and risk being viewed in a negative light by the general public.
Whether or not these consequences of police tactics are a deliberate strategy, they will have long-reaching effects on the accessibility of protest to old and new activists alike.