Millions of these blocks are in use in UK and in practice I don't think too many problems arise. Most are used for very small loads, e.g computer, router, printer, desk lamp, telephone charger etc, or for clusters of audio/media entertainment units, so electrical stresses are very small. Whilst the blocks are obviously open to abuse the 13 amp plug fuse does protect from serious overloading.
The principal hazard if used for heavy loads is, in my opinion, from the cheaply produced contact arrangements. These are typically just bent up brass strips with little spring pressure and can soon overheat.
As for price, 4 way units are available from reputable suppliers, (CPC/Farnell), for around £2.
