Blowing Out the Margins

Pardon an O/T comment, but I noticed Anna Puma posting one of her frequent links above, and wondered...

Sherry McEvil got chastised the other night for a long link blowing out the margins for cell readers. Cob went in and edited it. Don't think Sherry's link was much longer than Anna's usual.

Sometimes people will type a long stretch of text (ARGGGHH...HHH) that will enwiden the boxes.

Wondering
a) just what the length-limit is, about, any idea? and
2) if there's a difference if a link contains something, e.g. hyphens, browsers can use to wrap on? (Anna's, at least, wrapped in my Opera browser.)

Wrap = divide across lines, FYI.