There are two issues here, the issue of reverse profile and it's implications, and the issue of the saw-dive, which is different.
Let's start with reverse profile:
The problem with reverse profile, is mostly when diving with tables. The tables are based on mathematical models that were developed according to several assumptions, that had to be assumed in order to make a table that is workable. One of the assumptions was that you alwais dive the deeper dive first, than the shalower, never deeper than the last dive. The reason is within the model, It simply is different if you do it the otherway, and than we'd have to use several tables, that would make buisness a lot more confusing. That is most of it, but not all. There are people that also claim that in reverse profile the absorption of niterogen is greater. I don't like this theory, but it exists. When diving with computers, it depends on the kind of computer. Generaly, no computer manufacturer encourages reverse profile, for obviouse reasons. Still, when using newer computer, aspecialy those that use RGBM algorithms (i.e the newer SUUNTO computer, from the Vyper generation and on).
Saw profile:
When diving according to tables, you plan the dive according to the deepest deapth. So if most of the dive you were shalower, becouse you went up and down several times, logically, your body will not absorb more niterogen than it would if you did an exact square dive. If you use a computer, that is not an issu at all, so mostly, it dosen't matter if you don't do it to rapidly and keep a slow ascent rate. But...
There is another issue that get's here. If you happen to have already micro bubbles formed in you blood, which in themselves are not dangerouse usualy (and are, infact a very common thing. research showed, I belive, that about 100% of dives to 30 meters for longer than 5 minuets coused micro bubbles), it get's tricier. When you bounce up and down in the dive, you couse the bubble to grow and shrink. This couses it to grow in mol (number of molecules), that, aventualy, will couse it to grow in size when ascending. This of course can be a problem, aspecialy if you had another dive earlier, that was deep, or it's the end of a deep dive and you'r bouncing in the shallow water (very not recommended!). This is why we have to ascend very slowly. It was found that when ascending at 30 F/M the bubbles are kept at bay.
To conclude-If you do a shalow dive, with no prior dive, it wouldn't matter much (there's no risk of decompression under 6 meters anyway). If you do a deep dive and bounce a bit at the bottom, not to radicaly, it's also ok. If you do a dive, and bounce a lot, but keep a slow ascent rate in the bounces (I belive that descent rate in such a case is also of importance, but I havn't found anything about it), you probobly will be ok, but personnaly, I wouldn't do it. Than, if you did a long deep dive, than went to do a shallow dive, bounced a lot, surfaced a bit, didn't notice how fast you do it, you get into quite a risky position.
So- If you dive, and surface to check your position once or twice, keep a slow ascent rate, it's ok, better than getting lost. If you surface after a dive, to discover you'r far from the boat, than descent to 2-3 meters to swim, it's alo probobly ok.
