All (?) [edit: I stand corrected: only some] of which rely on A Big SAN, which falls under the "vertical" classification, i.e., scaling-by-throwing-money-at-it. Which is fine as long as you're aware that your price/performance sucks, and as long as your SAN is big enough.
No, most of the scalable SQL databases are shared-nothing.
... A little more looking shows that while some systems, like Oracle RAC (the one I'm most familiar with) and Sybase, do rely on shared storage, many do not. Sorry to generalize from insufficient data!
You can have a shared-nothing architecture using traditional "shared-everything" RDBMS.