I did look up Protagonist, and there are very few (but far, far fewer than 150), but no Hiro. I'm guessing that was a name that was used up while SL was still pay for a lifetime membership, as I came in just barely after. And, really, I'm quite old when it comes to Second Life, even if I haven't been there for quite some time, a couple of years is millenia in digital worlds. I do wonder if Hiro was even an option though, as I could see it causing some Drama.
When I'm not building in random spots that allow it, I tend towards the sandbox at the Ivory Tower of Primitives. It's got a large sandbox, although it is often plagued by rude people (for instance, someone rezzed a house directly behind me while I was playing with something, and then just left...leaving this huge yellow monstrosity taking up a sizeable chunk of the sandbox). There's a stonehenge you can see just beyond the bounds of one area of the sandbox, and I visited it today. Upon touching the correct stone, and then destroying the little ring, I was teleported to this odd little area, straight up, above the fly height, on the intersection of 4 sims. It was simple, and plain, and still one of the experiences I've had so far that has reminded me most of Second Life's potential...and I'll bet it's been here almost from the start (admittedly, the MUDish quality is some of what really grabbed me, and that it required actual interactivity- participation, not just observation). We're limited by our imagination here, and what do we have? Casinos, nightclubs, malls are where everyone is.
I've actually managed to avoid the vast majority of the virtual sex going on, the only time I've witnessed anything more than the sale of items for (and there is that free bed I picked up at YadNi's Junkyard, that, well, let's just say that that's one item I'm not tearing apart to inspect, and have instead destroyed because I didn't want to jizz stains on me, thanks) was when I first joined SL, and walked in on a group orgy, which was somewhat comical since all the attachments wouldn't texture, but instead it was avatars whose skins I could see, and then a vast expanse of uniform tan where I could almost make out shapes if I really tried. And there...I didn't. All the press suggests that there isn't anything to SL other than sex, and honestly, I think they're wrong. Yes, you're going to find some of it, because people who have the freedom to indulge in an unusual kink with people who are into the same thing will, as well as the ability to indulge in those which aren't possible in real life, be it due to legal or physical restraints. But, as much as that song that spawned endless machinima insists, the internet is not for porn (even if the first thought upon seeing that "You have reached the end of the internet" commercial was, "Wow, that guy has seen a lot of porn"). Neither are books defined by "erotic literature" and bodice rippers, nor are movies defined by pornos. It's getting a lot of press because it is there, and it is such a taboo, and it makes sensationalist news. As far as it getting the "mature content" sticker, it's the lowest common denominator of "adult," and in fact lends towards immaturity quite often.
There are some really great spaces in SL. Take the expansive empire of Caledon, for instance, spanning multiple sims, with a thematic umbrella encompassing all sorts of views. There's also the Wastelands, although I haven't really explored there much (in fact, my earlier building when I was assaulted by the yellow house was while I was trying to outfit myself such that I felt more comfortable there. I haven't explored Caledon a great deal yet either, I'm both saving it to savour, only going on short jaunts to better appreciate it, and I'm not particularly well attired for such a place yet either). There are numerous RPG sims of various themes, game sims (although I'm not really into the shoot-em-ups, I prefer the puzzles- especially with the limited interface allowed by SL. The lack of key bindings for actions pretty much kills all potential game development for me, even though Linden Labs touts SL as a platform for game development. The lack of a decent interface makes it all rather awkward and not worth it, to me), art galleries, all sorts of strange and wonderful places. They're beautiful, and engaging, and what Second Life should be, not a consumer wasteland of malls and casinos filled with afk zombies.
I have started the Mata Hari quest, but after a quite run I've already hit a wall at the Bannister. I'm wondering whether I'm on the wrong track, as I haven't seen any photographs of the runner, or landscapes that I recognize as the other's style. (I've also inspected the bannisters themselves under the assumption that I might be looking for entirely the wrong thing, but that has so far revealed nothing of interest.) However, as frustrating as getting stuck is, I recommend it to anyone in Second Life, even if you aren't going to wear the jewelery that you collect during it, as it is one of those examples of what Second Life can, and should, be.