Since uggs is a winterboot it's pretty obvious that it will be searched for in winter time. If you take this into account the graph shows a slow and steady increase in uggs searches.

Interestingly it seems that uggs are more popular in the northern hemisphere since there are not a lot of searches in what is the northern hemispheres summer and the southern hemispheres winter.

Accorindg to the theory they should have a good chance at making a valuable brand, since their growth is slow but has been increasing over the last four years.

http://en.wikipedia.org/wiki/Ugg_boots

Will it explain this? -- http://google.com/trends?q=twitter