Disclaimer: this isn't as good as the grind post, and I'm not sure it's even worth putting up. Anyway...
Runescape, despite having a relatively small world (20 minutes to run from end to end), has a vast variety of teleports. Seriously. It's loads. These teleports make any area exceptionally accessible to the average player, and form a convoluted network with no clear boundaries. Since new teleports are added constantly to different areas as they become relevant, one may assume that the abyss (the fictional explanation for teleportation) is truly, as Mod Osborne said, riddled with holes "like Swiss cheese".
This may not entirely be detrimental: unlocking faster travel is a rewarding and enjoyable experience, and the other gains of teleportation like increased safety, the ability to funnel players away from boring areas, and the chance to encourage players to use specific places more, cannot entirely be a bad thing. However, it has had several negative consequences, and some of the effects of teleportation are both good and bad in this regard.
This isn't rocket surgery: teleport effects are obvious. Here's a big one: travel isn't intuitive. If people want to know the best way to get somewhere, suddenly the answer is not "just run or use this specific list of spells/gems/mushrooms", it's "look it up". Teleports are too convoluted for most people to know them all, so they don't. This takes the players out of the game (reducing immersion), but could encourage social gameplay and communities who help each other in things like this.
Second obvious thing: it reduces the effect of distance on the economy. This, combined with the Grand Exchange, makes supply and demand on a small scale pointless. It would not be cheaper to buy, for example, elf mcguffins from players at their source in Tirannwn and bring them to the grand exchange to sell for a profit, because anyone can just teleport back and forth. This removes a potentially fun aspect of gameplay.
A third thing: it makes the map seem bigger. This isn't perhaps so obvious, but when you don't run through everything, you don't notice that the areas between different facilities are incredibly small. Since increased draw distance from html5 further reduces this, it isn't as much of a big deal.
Teleports reduce credibility of the world. If I can get anywhere in seconds, why does anyone sit still? They don't even try to explain lodestones. And who is giving out capes and rings with custom teleports? How do they make this stuff? If it's cheap enough to give away this stuff, can't I make my own?
Teleports are boring, and discourage exploration and running around seeing the world, because it's less interesting and less efficient.
So what can be done? I believe nothing. This is a classic example of power creep gone too far: what was once a fairly simple and reliable system now makes little sense and is a monster of epic proportions, but one that helps the player. Without annoying players hugely by getting rid of most teleports, one cannot affect the teleports system helpfully.
If I could make RuneScape, I'd do a lot of things very differently. Firemaking and slayer, for example, wouldn't be skills. Grind would be vastly reduced (I'd have started by making the level and experience cap 60, and working up from there). Summoning would have been implemented in a very changed manner. But the point of this article is to discuss teleports, so here's what I would have done.
Separate teleports from the combat skill, magic. It is strange and somewhat unfair to allow one combat class much better travel. Second, make teleports out of combat impossible. Teleports should require time, concentration, and a lack of pressure. Third, I'd make only one 'teleport from anywhere', and it'd go to a single, inconvenient place. Some sort of central town, without a lodestone of its own. Finally, I'd make only one teleport network: the lodestones. You have to touch them to activate them, you can only travel from one to the other, and I'd set up a clear story basis for them. They'd be at the centre of every major city, but none of the minor ones.
So, what would this create? A game where travel in the wilds was inevitable and necessary, but where cities were a refuge from danger, and well worth travelling towards at least once. A game where teleports were a privilege, and an extremely limited factor (which is only logical). A game where teleports made sense, but weren't being used all the time. I think it'd be a better game. Although it might not be recognisably runescape.
Besides, ideas are nothing. Execution is the King.