MMORPG stands for Massively Multiplayer Roleplaying Game. Usually the game consists of heavy borging consisting of finding the best ratio of xp/loot for time spent. There is some skill involved as you have to be constantly gaining xp and gold to advance in the game. Many people begrudge this system and state that it's not really a roleplaying game to commit mass genocide on orcs, goblins, and trolls until you finally have enough xp to level.
Similarly, people begrudge using links as a tool to determine search engine placement and that links aren't the best criteria to use to determine search engine placement. But alas links are the primary ranking factor and so we are left with Google the MMORPG.
Natural links are like roleplaying bonuses and like in MMORPG's are rare and too small in comparison to what you can achieve by borging links(or goblins). Plus, it's hard to get roleplaying bonuses unless you're of sufficient level(visibility in the search engines) for people to notice you.
In an MMORPG, you can either go after high level monsters or go after high plus low level monsters. You kill some low level monsters while you're waiting for healing in between beating down high level monsters all the while trying to increase your xp+gold per hour. Some people only go after low level monsters like what occurred during the World of Warcraft episode of South Park. Many MMORPG players consider this lame but it can be very effective based on what skills and abilities you have(usually a way to move very fast). This is like how some search engine optimizers achieve ranking by easy to come by links like social bookmarks. They can churn out a bunch of links very quickly and can rapidly advance in levels(Page Rank).
In many MMORPG's you have to wait for mobs to repop. This is similar to the C-class ip or domain issue that ocurs in SEO. Many say that only 10 C-class ip's count to a single domain. Most people who say that are building mini-sites and it doesn't make sense for internal linking as Google counts internal links on a blogger blog against your blogspot domain links as well. It doesn't make sense that a large site would have only 10 C-class ip restriction.
Anyways, it's clear that there is a some sort of domain/C-class ip factor in the ranking and that how many links it counts per domain depends on anchor text/which page is linked to/how many different ip's over all/site size/domain age/etc. Like in an MMORPG you have to wait for the mob's to repop, you have to wait for certain factors to occur before you can get more xp from links from the same domain.
In SEO, it's also beneficial to build links to your links. This is like having a second character in an MMORPG. If you can perform two things at once in an MMORPG, you can use a second character to heal or another to get you items that are only accessible to low level characters. In SEO, a second domain allows you to get easy links quickly just as in an MMORPG a second character may have easy starting quests that have good gold/xp per hour that you can transfer to your main character.
Alternative analogy would be that low level monsters don't have special attacks. Let's say Wikipedia is a level 9 monster with the special attack of no-follow. It's hard to beat that Wikipedia monster. Let's say monsters can get xp by killing other monsters. Let's say you have a beastmaster like character that can control other monsters and eventually let them free before proceeding to kill them for xp. If you get those monsters leveled up to level 9, then you can create an easy level 9 monster to kill without those special attacks.
Losing links is like dying in an MMORPG and losing levels. Buying links is like hiring people to farm gold. Getting a script to run your character is like a getting a script to automate your linkbuilding.
Anchor text is like having a sub-class. Let's say you are a thief with an assassin sub-class. If you are an assassin sub-class you only get xp in that sub-class with backstab. Links with the proper anchor give you xp in that sub-class(anchor) but any link gives you xp overall. Going back to the monster leveling analogy(this is probably stretching the analogy at this point), the monsters can achieve subclasses too. If a monster is highly leveled in the assassin subclass, you get more xp for backstabbing that monster(links with an anchor text from a page that receives a lot of links from the same anchor text gets a bonus).
Many times analogies are a stretch but linkbuilding and MMORPGs are incredibly analogous too each other. You can even use some terms interchangably like xp with link juice or PR with levels.