Q:

What's an example of a group with equivalent uniform structures where multiplication is not uniformly continuous? 

Say we have a topological group $G$.  It's easy to see that if $\cdot: G \times G \rightarrow G$ is uniformly continuous (with respect to either the right or left uniformity), then $G$ must have equivalent uniform structures.   I figure the converse is probably false, on the basis that otherwise I would have seen this mentioned somewhere.   But I can't think of an example, because I don't know many examples of topological groups, and all the examples I can think of with equivalent uniformities are built out of compact, abelian, or discrete groups, all of which do have uniformly continuous multiplication!   Can anyone give me a counterexample?   Or are these indeed equivalent? 

A:

Disclaimer: I haven't done the exercise carefully myself (and I'm not really in the mood to), but on Harry's request I'm posting it as an answer. 

According to Exercise 1.8.c on page 79 of Arhangel'skii-Tkachenko, Topological groups and related structures,  the following are equivalent for a topological group (uniformly continuous means uniformly continuous with respect to both the left and the right uniform structures):

The multiplication map $G^{2} \to G$ is uniformly continuous. 
The multiplication map $G^{n} \to G$ is uniformly continuous for all $n \geq 2$.
The group is balanced in the sense that the left and right uniformities are equivalent. 

Since you're interested in $3 \implies 1$ that's good enough (provided that it is true).