Number of attributes a character uses

Depends on the build and the profession but mostly 2-3.
Meaning primary profession only with maybe a few skills that are efficient with no attribute points (GoLE on monk for example) or are unlinked.

I like to run 3 or 4. My 3 spreads are usually 11-10-10, with 11 being any non-primary attribute. With 4, I run 10-10-8-8.

I think being able to get a lot of use out of a utility skill with the cost of having a hex or two end a bit sooner is entirely worth it. If you desperately need to hit a breakpoint, run major runes.

USually 3. ....

2-3.

Ele I use only 2 really, (elemental att and E-storage)

Usually 3, but my el has been going water and energy storage only lately.

All of my PvE characters spec into 3 (12+10+8), except for my first character, who sometimes dips into all 4 Ranger attributes (11+9+8+8).

Some hero builds I use only use 2 main attributes (12+12+3), like Smiting Monk and SF Ele.

Mindblast is a fire skill.

I disagree with 4 being "ineffective".
In early factions GvG Blessed-light monks with Divine, Prot, Heal and Domination (hex breaker) were really popular.

After that it gets a bit messy though
some valid spreads for 5 attrib lines;
10 8 8 8 7
10 10 10 4 3

some valid spreads for 6;
10 9 7 6 6 6
10 8 8 7 6 5

I don't think I ever run just 2 attribs.
The cost of 11->12 is 20 points. Bearing in mind 0->6 is only 21 total, throwing in a utility skill is probably the better bet.

Edit: Rather than bump I'll reply to poster below me here.
Aye, I'm not condoning using 5+, just pointing out that you can still get respectably high attrib values with such a spread.

Blue, if you're running 6 attributes, you're running about 1 skill per attribute line, bearing in mind that you're (hopefully) bringing a res too. There is more than 1 good skill per attribute line, so it's just silly to spread yourself unnecessarily thin like that, when you could consolidate your points, be more effective at what you do, and have just as powerful (or more powerful, because of skill synergies) a bar.

Bringing a utility skill or two from a secondary profession is one thing; spec-ing 5 or more attributes is just dumb. Spec-ing 4 is - most of the time - a bad idea, unless the 4th att is just something you dump leftover points in, or it's a build that simply needs the 4th att (splinter barrage, for example).

I use 3-4 on monk and its been stated how that is distributed earlier in this thread.

Two to three, two focused on the main proffession and one for the second proffession.

2-4 depending on build. Sometimes a 3rd or 4th att is just leftover points into, say, air for shock on war.

For my Warrior I usually run with points in 2 attributes (Strength+ Weapon of choice) unless I'm running a W/R then it's 3 so I can put 9 into beast mastery for poisonous bite.

12 Marksmanship, 12 Expertise.
Secondary Mesmer for Epidemic, no points needed.

Except for farming builds (55 monk, etc.) I never run more than 3. If I use skills from more than 3 attributes, they either do not neet attribute points to be effective (Mending Touch, etc.) or they are No Attribute skills (Epidemic, etc.).

I find being highly effective at 2-3 attributes does better than being marginally effective at 3-5.

usually 2 or 3,
on my ele 2: fire + energy or air+ energy

2 to 3, but often the third one is made up of left over points.

. 2 or 3

2 or 3 for effective point distribution. Usually 16 curses, 12 SR and the remaining blood for a typical SS FoW build with BR, runes included. But I haven't used that in a while, I've been playing SV a lot lately...

3-4 here...I almost always run 3 (I'm in love with the 11-10-10 combo), but every once in a while I'll deviate and run 4.

I just hate seeing those extra attribute points wasted...

Ranger it depends, 3 in ab and ra, 2 everywhere else.
Elementalist, 2 or 3 depending on the build
Warrior, 3 in pvp, 2 in pve
Necromancer, 3 (sometimes 2, but not very often)