As far as socketing your shako, yes a lot of people do, especially if you're a MF fanatic.
The new patch allows unique armors and weapons to be upgraded (normal to exceptional, exceptional to elite). Shako's cannot be upgraded since they are already elite items, but for other items, the recipe is as follows:
To make a normal unique weapon exceptional: 1 Ral/1 Sol/1 Perf Emerald
To make an exceptional unique weapon elite: 1 Lum/1 Pul/1 Perf Emerald
To make a normal unique armor exceptional: 1 Tal/1 Shael/1 Perf Diamond
To make an exceptional unique armor elite: 1 Ko/1 Lem/1 Perf Diamond
Examples of normal to exceptional to elite would be:
Cap to War Hat to Shako, or Crystal Sword to Dimensional Blade to Phase Blade.
If I messed up the cube recipes anywhere, someone please let me know, but I think they are correct.
Edit: I forgot to mention that you can do this with rare items also- not just uniques. The cube recipes are different, but I assumed you were talking about uniques.
In response to what you should socket your Shako with, it depends on what you use the character for. If you are purely MF then stick a PTopaz in it. If all you want to do is kill, whether PvP or PvM then socket your Shako with a Rainbow Facet jewel that matches your build.
If i PTopaz my shako and vipermagi, my totals will be as follows:
MF = 236
Resists=Fire/Cold maxed Lightning really close. Poison in the 50s
Gonna go for that for now but I can always use a rhyme, 27% mf ammy, and some rare gloves and rare ring and get my mf up to 320+ but then I drop 3 more skill points. (resists still about the same). Gonna experiment and see what happens.