There's a lot of ceramic blades and obviously steel, but in the week or so that I've been browsing, I've only seen one full titanium knife.
Isn't titanium better than steel for everything?
There's a lot of myths surrounding titanium. Firstly, as we're discussing, it makes for a very poor blade material. The most common alloy is 6Al4V (6% aluminum, 4% vanadium), and while it's very strong and light, it sucks for knife blades. It really can't be heat treated, it's soft and when you get down to the edge, it's weak and brittle for cutting applications. The advantages are that it's light, non-magnetic, and won't rust (there's no iron) or otherwise destructively oxidize (all titanium in fact instantly oxidizes, just like aluminum, but the layer of oxidization doesn't corrode or discolor). This makes it a good choice for hold-out, last ditch self defense knives (where you only need to make a cut/stab or two), diving knives, and Navy divers who need to disarm magnetically activated mines. But for a tool that gets used daily, it's a bad choice.
Mission's Beta Ti is a slightly different beast; it can be heat hardened and is more suitable as a blade material, but at its best, it's comparable to the lowest quality flea market crap knife steels (and even then, the crap steel might outperform Beta Ti, and it's certainly easier to sharpen). If you absolutely MUST have a working knife made from Ti, Mission is the way to go.
If you simply want a blade that won't ever rust (magnetism and weight be damned), there's better options than titanium. One is Stellite 6k or Talonite, which are cobalt alloys. They're harder than titanium, softer than all but the softest knife steels, but it's greatest property (other than being rust-proof) is it's slickness. Because it's so slick, it doesn't dull as quickly because there's less friction. So even though it's softer, its edge retention is as good as most any mid level blade steel. They use these cobalt alloys in the blade fans of jet engines because they wear down less than aluminum, steel, or titanium (air friction can actually grind away at the blades in jet engines). If Stellite 6K or Talonite is just too expensive (it is expensive, and quite difficult to work with), there's the very economical option of H1 or X1.5 steels (which use nitrogen instead of carbon) used by Spyderco and Benchmade. Despite being mostly iron, these "steels" simply will not ever, ever rust.
The other myth regarding titanium is in how strong it is. Titanium is not necessarily stronger than steel. Steel of the right alloy, with the right heat treatment will always be stronger than titanium. So if strength is what you want (weight be damned), steel will be the way to go. Where titanium has the advantage is in the strength-to-weight ratio. The easiest example to look at (for me, anyway) is in bicycle frames. The 3 most common metals used are aluminum, steel, and titanium (there's also scandium, and of course carbon fiber, but that's not what we're talking about here). A steel frame will always be stronger. Theoretically, you could make a titanium frame stronger than a steel frame by using more titanium, but that defeats the point in having a titanium frame in the first place. Titanium is used in some bikes because you can make a very strong frame (and other components)--stronger than aluminum--lighter than a steel one. Aluminum is commonly used (extremely common) because it's much lighter than steel, and sufficiently strong. The advantage of using titanium over aluminum is weight and strength, but it's far, far more expensive. Titanium also has different properties that make for a different ride (titanium is a lot springier than Al, steel, or CF). For example, on a rigid frame (no suspension) single speed, a Ti fork will absorb more shock than a steel fork, but it'll be bouncier. This comes down to personal preference. Anyway...
The myth of superior titanium blades will continue because the myth perpetuates itself. People who make movies don't know better, or if they do, they assume the audience won't. For example, Wesley Snipe's silver-etched titanium sword in the "Blade" movies. Also, there's the Shick Quattro Titanium razor blades. Pay attention to the commercial. They say the blades are titanium. They're not. They're steel, like any other razor blade, but coated with titanium nitride (TiN), which is a common knife blade coating, and also used on high-speed tools for machining. But the public doesn't know WTF titanium nitride is, and titanium sounds "cool" (because of people who believe the myth), so that's what they say in the commercial.