4. Visa "limits" are vastly excessive & overly elastic.

(According to USCIS: Section 416(c)(1) of ACWIA (8 USC § 1184 notes) mandates a report "...of the numbers of aliens who were issued visas or otherwise provided non-immigrant status under section 101(a)(15)(H)(i)(b) of the Immigration and Nationality Act during the preceding 3-month period".   Furthermore, as described in section 416(c)(3), this report "...shall include the number of aliens who were issued visas or otherwise provided non-immigrant status pursuant to petitions filed by institutions or organizations described in section 212(p)(1) of the Immigration and Nationality Act (as added by section 415 of this title).")
 

The numbers of visas actually issued, OTOH, is what matters.   These numbers are available in the State Department's annual reports:
year	issued
1996	58,327
1997	80,547
1998	91,360
1999	116,513
2000	133,290
2001	161,643
2002	118,352
2003	107,196
2004	138,965
2005	124,099
2006	135,421
2007	154,053
2008	129,464
2009	110,367
2010	117,409
year	issued

DoS
FY2004-2008 pdf
FY2006 table 16A pdf, table 16B pdf
FY2007 table 16A pdf, table 16B pdf
FY2008 table16A pdf, table 16B pdf
FY2009 table 16A pdf, table 16B pdf
FY2010 table 16A pdf, table 16B pdf
Note: These numbers leave out visas issued after an initial rejection and subsequent successful appeal or waiver.   In some cases these amount to tens or hundreds of thousands of additional visas, and 26,802 more H-1B visas in FY2008.   This brings the actual total H-1B visas initially issued, renewed and extended in FY2008 up to 156,985.

For prospective H-1B workers already residing in the United States (on H-1B or other visas), USCIS updates the workers' visa status without involvement from State.

IMMACT1990 supposedly required H-1B applicants to have "specialized knowledge", though required no proof of such knowledge, while PL108-77 and PL108-78 required the H-1B1 visas set aside for those from Chile and Singapore to have "highly specialized knowledge", while requiring no proof of such knowledge, and allowed indefinite stays in the USA.

There are usually a few thousand unclaimed visas each year, primarily from the sub-categories set aside for Chile and Singapore.   USCIS says they roll these over, adding them to the 58,200 general allotment for the next year.

Hundreds of H-1B visas have gone to people without the equivalent of a US high school diploma, and thousands to those without the equivalent of a US bachelor's degree.

new H-1B visas by degree

year	no HS diploma	HS	<1 year college	1+ year college	Associate's	total
2000	554	288	158	1290	696	2986
2001	247	895	284	1376	1181	3983
2002	169	806	189	849	642	2655
2003	148	822	122	623	534	2249
2004	123	690	137	421	432	1803
2005	107	440	77	358	363	1345
2006	96	392	54	195	177	914
2007	72	374	42	210	215	913
2008	80	174	19	175	195	643
2009	108	190	33	236	262	829
2010	140	201	24	213	161	739
year	no HS diploma	HS	<1 year college	1+ year college	Associate's	total

"Since 1999, the United States has approved enough H-1B visas for computer workers to fill 87% of net computer job growth over that period.   Since 1999, the United States has had a net loss of 76K engineering jobs.   Over the same time period, the United States has approved an average of 16K new H-1B visas each year for engineers.   If current employment trends continue and the H-1B quota remains unchanged, the United States will approve enough H-1B visas for computer workers to fill about 79% of the computer jobs it creates each year." --- 2008-06-15: John Miano

There was no shortage of talented US citizen STEM workers.

There is no shortage of talented US citizen STEM workers.

No credible evidence of impending shortage of talented US citizen STEM workers has been produced.