Northern Brewer/Midwest has come under a lot of pressure as of lately regarding their glass Big Mouth Bubbler product line. They've confirmed that they are curating their reviews that are submitted to the site. If they are negative, they claim to contact the reviewer personally to resolve their complaints and remove the negative review.
If you do a search for the product on Northern Brewer's website and Amazon, you'll see two very contrasting sets of ratings. There is not one mention of it shattering on their review system, and just about every review on Amazon makes mention of it.
People have gone to the E.R. over the Big Mouth Bubbler (blood warning). Consider yourself very fortunate. Many people have reported malformations in the glass since they are individually hand blown. Others claim they don't sit up straight, but the one common trend all have claimed is how thin the glass is. One person even claimed to have seen it flex and wobble when it's full of liquid; something glass should never do!
It shattering on you has little to do with wear and tear, and more with poor construction. The common advice to homebrewers is to not purchase the glass Big Mouth Bubbler. I've heard of no less than 10-20 complaints regarding them all shattering. Do your fellow homebrewers a favor and alert them to this, you may be saving them a very dangerous, even deadly investment. I've also heard a lot of complaints about the poor quality of the plastic version as well, particularly with the lid being difficult to work with. At least the plastic version won't kill you your send you to the E.R. with lacerations.
Contact Northern Brewer/Midwest and have them either refund you or send a plastic replacement. They're support is a stark contrast to this product. I've heard nothing but praise regarding their customer support. It's unfortunate that when it comes to your health and safety (and that of those around/under you when things go awry), the same cannot be said regarding their product, which they are marketing very, very hard.
EDIT: For those showing up late to the game, it would appear that Northern Brewer/Midwest removed their glass Big Mouth Bubblers from Amazon (still available on their own websites), and one can only speculate the cause being the overwhelming negative reviews it received (last time I saw, it was hovering between one to two stars out of five). It would seem that they also have begun to allow one or two (literally, that's all) negative reviews of their products exist on their own sites, again speculating that it's to cover their bases and give the appearance that they don't delete (cough every one of cough) their negative reviews. The advice still stands. Do not buy this product.